NCERT Formula Library
Formula Library
Real NCERT formulas linked directly to their chapter — every entry opens the same verified page students see while learning that chapter.
Mathematics
272 formulasTime
Class 1Days in a Week
1 week = 7 days
Monday, Tuesday, Wednesday, Thursday, Friday, Saturday, Sunday
Time
Class 1Months in a Year
1 year = 12 months = 365 days (or 366 in a leap year)
January to December
Numbers from Ten to Twenty
Class 1Teen Numbers
10 + ones digit = teen number
Numbers 11-19 are called "teen" numbers
Numbers from Ten to Twenty
Class 1Place Value
Any 2-digit number = (tens × 10) + ones
13 = (1×10) + 3 = 10+3 = 13
Subtraction
Class 1Subtraction
Whole - Part = Remaining Part
You cannot subtract a bigger number from a smaller number in Class 1
Subtraction
Class 1Subtraction Fact
If a + b = c, then c - b = a
Since 3+4=7, we know 7-4=3 and 7-3=4
Numbers from One to Nine
Class 1Counting Rule
Count each object once and only once
Always count from left to right or top to bottom to avoid missing any
Addition
Class 1Addition
Part + Part = Whole
The order does not matter: 3+4 = 4+3 = 7
Addition
Class 1Adding Zero
Any number + 0 = that number
Zero is the identity for addition
Money
Class 1Change Calculation
Change = Amount Given - Cost
Cost ₹7, gave ₹10, change = ₹10 - ₹7 = ₹3
Money
Class 1Paise to Rupees
100 paise = ₹1
250 paise = ₹2 and 50 paise
Real Numbers
Class 10Euclid Division Lemma
a = bq + r, 0 ≤ r < b
Used repeatedly to find HCF.
Real Numbers
Class 10HCF-LCM Relationship
HCF(a, b) × LCM(a, b) = a × b
For 12 and 18: 6 × 36 = 12 × 18 = 216
Real Numbers
Class 10Terminating Decimal Test
If q = 2^m × 5^n in lowest form, then p/q terminates
3/40 terminates because 40 = 2^3 × 5
Polynomials
Class 10Sum of Zeroes
α + β = -b/a
For x² - 5x + 6, sum of zeroes = 5
Polynomials
Class 10Product of Zeroes
αβ = c/a
For x² - 5x + 6, product of zeroes = 6
Polynomials
Class 10Cubic Relation
α + β + γ = -b/a
For ax³ + bx² + cx + d, sum of zeroes depends on coefficient of x²
Pair of Linear Equations in Two Variables
Class 10Unique Solution Condition
a₁/a₂ ≠ b₁/b₂
If ratios of x and y coefficients differ, the lines intersect once
Pair of Linear Equations in Two Variables
Class 10Infinite Solutions Condition
a₁/a₂ = b₁/b₂ = c₁/c₂
Both equations represent the same line
Pair of Linear Equations in Two Variables
Class 10No Solution Condition
a₁/a₂ = b₁/b₂ ≠ c₁/c₂
Both lines are parallel and distinct
Quadratic Equations
Class 10Standard Form
ax² + bx + c = 0, a ≠ 0
2x² - 7x + 3 = 0 is in standard form
Quadratic Equations
Class 10Quadratic Formula
x = [-b ± √(b² - 4ac)] / 2a
For x² - 5x + 6 = 0, roots are 2 and 3
Quadratic Equations
Class 10Discriminant
D = b² - 4ac
For x² + 2x + 1, D = 0 so the roots are equal
Arithmetic Progressions
Class 10nth Term
aₙ = a + (n - 1)d
If a = 3 and d = 4, then a₅ = 3 + 4×4 = 19
Arithmetic Progressions
Class 10Sum of First n Terms
Sₙ = n/2 [2a + (n - 1)d]
For a = 2, d = 3, n = 4: S₄ = 4/2[4 + 9] = 26
Arithmetic Progressions
Class 10Sum Using Last Term
Sₙ = n/2 (a + l)
If first term is 5, last term is 25 and n = 5, sum = 75
Triangles
Class 10Area Ratio of Similar Triangles
Ar(ΔABC) / Ar(ΔPQR) = (AB / PQ)²
If corresponding sides are in ratio 2:3, areas are in ratio 4:9
Triangles
Class 10Pythagoras Theorem
a² + b² = c²
For sides 3, 4, 5: 3² + 4² = 5²
Triangles
Class 10Basic Proportionality Idea
If a line is parallel to one side of a triangle, it divides the other two sides proportionally
Useful in many textbook proofs
Coordinate Geometry
Class 10Distance Formula
d = √[(x₂ - x₁)² + (y₂ - y₁)²]
Distance between (1,2) and (4,6) is 5
Coordinate Geometry
Class 10Midpoint Formula
M = ((x₁ + x₂)/2, (y₁ + y₂)/2)
Midpoint of (2,4) and (6,8) is (4,6)
Coordinate Geometry
Class 10Internal Section Formula
P = ((mx₂ + nx₁)/(m+n), (my₂ + ny₁)/(m+n))
Used when one point divides a segment in m:n
Introduction to Trigonometry
Class 10Basic Ratios
sin θ = P/H, cos θ = B/H, tan θ = P/B
In a 3-4-5 triangle with angle opposite 3, sin θ = 3/5
Introduction to Trigonometry
Class 10Identity
sin²θ + cos²θ = 1
If sin θ = 3/5, then cos θ = 4/5
Introduction to Trigonometry
Class 10Derived Identity
1 + tan²θ = sec²θ
If tan θ = 3/4, then sec²θ = 25/16
Some Applications of Trigonometry
Class 10Angle of Elevation Model
tan θ = height / horizontal distance
If θ = 45° and distance = 20 m, height = 20 m
Some Applications of Trigonometry
Class 10Angle of Depression Link
Angle of depression from the top equals the corresponding angle of elevation from below
This equality helps convert many observation problems
Circles
Class 10Radius-Tangent Property
Radius at the point of contact ⟂ tangent
If PT is tangent at T and OT is radius, then OT ⟂ PT
Circles
Class 10Equal Tangent Lengths
PA = PB
If tangents from P touch the circle at A and B, then PA = PB
Areas Related to Circles
Class 10Area of Circle
A = πr²
If r = 7 cm, area = 49π cm²
Areas Related to Circles
Class 10Circumference
C = 2πr
If r = 7 cm, circumference = 14π cm
Areas Related to Circles
Class 10Area of Sector
Area = (θ/360) × πr²
If θ = 90° and r = 14 cm, area = 49π cm²
Surface Areas and Volumes
Class 10Volume of Cylinder
V = πr²h
For r = 3 cm, h = 10 cm, volume = 90π cm³
Surface Areas and Volumes
Class 10Volume of Sphere
V = 4/3 πr³
For r = 3 cm, volume = 36π cm³
Surface Areas and Volumes
Class 10TSA of Cylinder
TSA = 2πr(h + r)
For r = 2 cm and h = 5 cm, TSA = 28π cm²
Statistics
Class 10Mean
Mean = Σfx / Σf
Multiply each class mark by frequency and divide by total frequency
Statistics
Class 10Mode
Mode = l + [(f₁ - f₀) / (2f₁ - f₀ - f₂)] × h
Use the modal class and neighbouring frequencies
Statistics
Class 10Median
Median = l + [(N/2 - cf) / f] × h
Find the median class using cumulative frequency first
Probability
Class 10Basic Probability
P(E) = n(E) / n(S)
If 3 outcomes are favourable out of 8 total, probability = 3/8
Probability
Class 10Complement Rule
P(E) + P(not E) = 1
If P(E) = 0.35, then P(not E) = 0.65
Binomial Theorem
Class 11(a+b)ⁿ = Σ ⁿCr aⁿ⁻ʳ bʳ
(a+b)ⁿ = Σ ⁿCr aⁿ⁻ʳ bʳ
Complex Numbers and Quadratic Equations
Class 11i² = -1
i² = -1
Complex Numbers and Quadratic Equations
Class 11|z| = √(a²+b²)
|z| = √(a²+b²)
Complex Numbers and Quadratic Equations
Class 11Quadratic formula
Quadratic formula
Conic Sections
Class 11Circle: x²+y²=r²
Circle: x²+y²=r²
Conic Sections
Class 11Parabola: y²=4ax
Parabola: y²=4ax
Conic Sections
Class 11Ellipse: x²/a²+y²/b²=1
Ellipse: x²/a²+y²/b²=1
Limits and Derivatives
Class 11d/dx(xⁿ) = nxⁿ⁻¹
d/dx(xⁿ) = nxⁿ⁻¹
Limits and Derivatives
Class 11d/dx(sin x) = cos x
d/dx(sin x) = cos x
Limits and Derivatives
Class 11d/dx(eˣ) = eˣ
d/dx(eˣ) = eˣ
Permutations and Combinations
Class 11ⁿPr = n!/(n-r)!
ⁿPr = n!/(n-r)!
Permutations and Combinations
Class 11ⁿCr = n!/r!(n-r)!
ⁿCr = n!/r!(n-r)!
Sequences and Series
Class 11Sum of AP = n/2(2a+(n-1)d)
Sum of AP = n/2(2a+(n-1)d)
Sequences and Series
Class 11Sum of GP = a(rⁿ-1)/(r-1)
Sum of GP = a(rⁿ-1)/(r-1)
Trigonometric Functions
Class 11Fundamental Identity
sin²θ + cos²θ = 1
Most important — used in almost every problem
Trigonometric Functions
Class 11Sum Formulas
sin(A+B) = sinAcosB + cosAsinB
cos(A+B) = cosAcosB - sinAsinB
sin75° = sin(45°+30°) = (1/√2)(√3/2)+(1/√2)(1/2) = (√3+1)/(2√2)
Trigonometric Functions
Class 11Double Angle
sin2A = 2sinAcosA
cos2A = cos²A - sin²A = 1-2sin²A
sin60°=sin(2×30°)=2×sin30°×cos30°=2×(1/2)×(√3/2)=√3/2 ✓
Trigonometric Functions
Class 11Product to Sum
2sinAcosB = sin(A+B) + sin(A-B)
2sin75°cos15° = sin90°+sin60° = 1+√3/2
Application of Derivatives
Class 12Slope of Tangent
m = dy/dx|_(x₁,y₁) = f'(x₁)
y=x³-2x at (1,-1): m=3x²-2|_{x=1}=3-2=1. Tangent: y+1=1(x-1)→y=x-2
Application of Derivatives
Class 12Equation of Normal
y - y₁ = (-1/m)(x - x₁) where m = f'(x₁)
At (1,-1) with m=1: Normal: y+1=-1(x-1)→y=-x
Application of Derivatives
Class 122nd Derivative Test
f'(x₀)=0 AND f''(x₀)<0 → local max | f''(x₀)>0 → local min
f(x)=x²-4x+3: f'=2x-4=0→x=2. f''=2>0 → local min at x=2, f(2)=-1
Application of Derivatives
Class 12Related Rates
Use chain rule: dV/dt = dV/dr × dr/dt
Sphere: V=4πr³/3 → dV/dt=4πr²×dr/dt. Given dr/dt=2cm/s at r=5: dV/dt=4π×25×2=200π cm³/s
Determinants
Class 12|A| = a(ei-fh) - b(di-fg) + c(dh-eg)
|A| = a(ei-fh) - b(di-fg) + c(dh-eg)
Determinants
Class 12A⁻¹ = adj(A)/|A|
A⁻¹ = adj(A)/|A|
Differential Equations
Class 12dy/dx = f(x)g(y)
dy/dx = f(x)g(y)
Differential Equations
Class 12dy/dx + Py = Q
dy/dx + Py = Q
Integrals
Class 12∫xⁿdx = xⁿ⁺¹/(n+1)
∫xⁿdx = xⁿ⁺¹/(n+1)
Integrals
Class 12∫sin x dx = -cos x
∫sin x dx = -cos x
Integrals
Class 12∫eˣdx = eˣ
∫eˣdx = eˣ
Inverse Trigonometric Functions
Class 12sin⁻¹(-x) = -sin⁻¹x
sin⁻¹(-x) = -sin⁻¹x
Inverse Trigonometric Functions
Class 12sin⁻¹x + cos⁻¹x = π/2
sin⁻¹x + cos⁻¹x = π/2
Matrices
Class 12(AB)T = BTAT
(AB)T = BTAT
Matrices
Class 12(A+B)T = AT+BT
(A+B)T = AT+BT
Probability
Class 12Conditional Probability
P(A|B) = P(A∩B) / P(B)
P(A∩B)=0.12, P(B)=0.4: P(A|B)=0.12/0.4=0.3
Probability
Class 12Bayes' Theorem
P(Aᵢ|B) = P(Aᵢ)P(B|Aᵢ) / Σ P(Aⱼ)P(B|Aⱼ)
Classic problem: factory machines producing defective items
Probability
Class 12Binomial Distribution
P(X=r) = ⁿCᵣ pʳ qⁿ⁻ʳ | Mean=np | Variance=npq
Coin tossed 5 times: P(3 heads)=⁵C₃×(1/2)³×(1/2)²=10/32=5/16
Probability
Class 12Total Probability
P(B) = Σᵢ P(B|Aᵢ)×P(Aᵢ)
Used when event B can happen via multiple paths A₁, A₂, A₃...
Three Dimensional Geometry
Class 12l²+m²+n² = 1
l²+m²+n² = 1
Three Dimensional Geometry
Class 12Distance of point from plane
Distance of point from plane
Vector Algebra
Class 12a·b = |a||b|cosθ
a·b = |a||b|cosθ
Vector Algebra
Class 12|a×b| = |a||b|sinθ
|a×b| = |a||b|sinθ
Counting in Groups
Class 2Multiplication as Repeated Addition
a × b = a + a + a... (b times)
Or: 3×5 = 3+3+3+3+3 = 15 (three added five times). Both give 15!
Counting in Groups
Class 2Commutative Property
a × b = b × a
4 × 6 = 6 × 4 = 24
What is Long, What is Round?
Class 2Shape Properties Summary
Cube: 6 faces, 12 edges, 8 vertices | Cuboid: 6 faces, 12 edges, 8 vertices | Cone: 2 faces, 1 edge, 1 vertex | Cylinder: 3 faces, 2 edges, 0 vertices
A die is a cube — count: 6 faces (each face has numbers 1-6), 12 edges, 8 corners
Jugs and Mugs
Class 2Capacity Units
1 litre (L) = 1000 millilitres (mL)
Large amounts use kilolitres (kL): 1 kL = 1000 L
Counting in Tens
Class 2Expanded Form
2-digit number = Tens digit × 10 + Ones digit × 1
This is called expanded notation
Counting in Tens
Class 2Place Value
Place value = Face value × Position value
In 73: place value of 7 = 7×10 = 70; place value of 3 = 3×1 = 3
Tens and Hundreds
Class 2Expanded Form (3-digit)
3-digit number = H×100 + T×10 + O×1
H=hundreds digit, T=tens digit, O=ones digit
Tens and Hundreds
Class 2Hundreds
10 tens = 1 hundred
10 groups of 10 = 100
How Much Can You Carry?
Class 2Standard Weight Units
1 kg = 1000 g
kg = kilogram, g = gram
Give and Take
Class 2Column Subtraction
Subtract ones first, then tens (borrow if top < bottom)
54-28: ones=4<8 so borrow; 14-8=6; tens=(5-1)-2=2; answer=26
Give and Take
Class 2Checking Subtraction
Answer + Subtracted number = Original number
54-28=26; check: 26+28=54 ✓
Add Our Points
Class 2Column Addition
Add ones first, then tens (carry if sum ≥ 10)
47+35: ones=7+5=12(write 2,carry 1); tens=4+3+1=8; answer=82
Footprints
Class 2Unit Conversion
1 m = 100 cm
km = kilometre: 1 km = 1000 m (for long distances like roads)
Long and Short
Class 3Unit conversion
10 mm = 1 cm | 100 cm = 1 m | 1000 m = 1 km
Convert from larger to smaller unit: multiply. Smaller to larger: divide.
Long and Short
Class 3Perimeter of Rectangle
P = 2 × (length + breadth)
Rectangle 8 cm × 5 cm: P = 2×(8+5) = 2×13 = 26 cm
Long and Short
Class 3Perimeter of Square
P = 4 × side
Square side = 7 cm: P = 4×7 = 28 cm
Fun with Numbers
Class 3Expanded Form (4-digit)
Th×1000 + H×100 + T×10 + O×1
Th=thousands, H=hundreds, T=tens, O=ones
Give and Take
Class 3Column Addition
Add ones first, then tens, then hundreds
Carry means a group of 10 is moved to the next higher place value
Give and Take
Class 3Column Subtraction
Subtract ones first, then tens, then hundreds
503 - 248 = 255 (3<8: borrow; 13-8=5; 0-1-4: borrow; 10-5=5; 5-1-2=2)
Who is Heavier?
Class 3Weight Units
1 kg = 1000 g
Scientific unit of mass is kilogram (kg)
How Many Times?
Class 3Multiplication
a × b = a added b times
Also: 6×4 = 4×6 = 24 (commutative)
How Many Times?
Class 3Multiply by 0
Any number × 0 = 0
999 × 0 = 0
How Many Times?
Class 3Multiply by 1
Any number × 1 = that number
45 × 1 = 45
Time Goes On
Class 3Time Conversion
60 seconds = 1 minute | 60 minutes = 1 hour | 24 hours = 1 day | 7 days = 1 week | 52 weeks = 1 year
2 hours = 2×60 = 120 minutes | 3 days = 3×24 = 72 hours
Can We Share?
Class 3Division
Dividend ÷ Divisor = Quotient
24 ÷ 6 = 4 (24 is dividend, 6 is divisor, 4 is quotient)
Can We Share?
Class 3Division-Multiplication Relationship
If a ÷ b = c, then b × c = a
If 15 ÷ 3 = 5, then 3 × 5 = 15
Can We Share?
Class 3Division by 1
Any number ÷ 1 = same number
67 ÷ 1 = 67
Fields and Fences
Class 4Perimeter of Rectangle
P = 2 × (l + b)
l=length, b=breadth
Fields and Fences
Class 4Perimeter of Square
P = 4 × s
s=side length
Fields and Fences
Class 4Area of Rectangle
A = l × b
Rectangle 8m × 5m: A = 8×5 = 40 sq m
Fields and Fences
Class 4Area of Square
A = s × s = s²
Square with side 6cm: A = 6×6 = 36 sq cm
Building with Bricks
Class 4Multiplication
Multiplicand × Multiplier = Product
23 × 14 = 322 (23 is multiplicand, 14 is multiplier, 322 is product)
Building with Bricks
Class 4Multiply by Powers of 10
N × 10 = N with one extra 0 | N × 100 = N with two extra 0s
56 × 1000 = 56,000
Halves and Quarters
Class 4Fraction
Fraction = Numerator / Denominator
In 3/8: numerator=3, denominator=8, meaning 3 parts out of 8 equal parts
Halves and Quarters
Class 4Finding Fraction of a Number
p/q of N = N ÷ q × p
3/4 of 20 = 20÷4×3 = 5×3 = 15
Tick Tick Tick
Class 424-hour conversion
PM time (except noon): 24-hr = 12-hr + 12
3:00 PM = 3+12 = 15:00 | 8:30 PM = 8:30+12 = 20:30
Tick Tick Tick
Class 4Time difference
End time - Start time = Duration
15:45 - 11:20 = 4 h 25 min
A Trip to Bhopal
Class 4Map Scale
Actual distance = Map distance × Scale factor
Map distance 5 cm, scale 1 cm = 50 km → Actual = 5×50 = 250 km
Shapes and Angles
Class 5Angle Sum of Triangle
∠A + ∠B + ∠C = 180°
If two angles are 60° and 70°, third angle = 180-60-70 = 50°
Shapes and Angles
Class 5Angle Sum of Quadrilateral
Sum of all 4 angles = 360°
If three angles are 90°, 90°, 80°, fourth angle = 360-260 = 100°
Shapes and Angles
Class 5Area of Rectangle
Area = length × breadth
Room 5m × 4m: Area = 5×4 = 20 m²
Shapes and Angles
Class 5Area of Square
Area = side × side = side²
Square with side 6 cm: Area = 6² = 36 cm²
How Many Squares?
Class 5Area of Rectangle
A = l × b
Area unit is always "squared" (cm², m², km²)
How Many Squares?
Class 5Area of Square
A = s²
7 cm × 7 cm = 49 cm²
Parts and Wholes
Class 5Equivalent Fractions
a/b = (a×n)/(b×n) for any non-zero n
3/4 = 6/8 = 9/12 (multiply by 2, then 3)
Parts and Wholes
Class 5Adding Fractions (same denom)
a/c + b/c = (a+b)/c
3/7 + 2/7 = 5/7
Parts and Wholes
Class 5Adding Fractions (different denom)
a/b + c/d = (a×d + c×b)/(b×d)
1/3 + 1/4 = (4+3)/12 = 7/12
The Fish Tale
Class 5Indian Number System
1 crore = 100 lakh | 1 lakh = 100 thousand | 1 thousand = 10 hundred
2,75,48,923 = 2 crore 75 lakh 48 thousand 9 hundred 23
The Fish Tale
Class 5Rounding Rule
If digit to the right is ≥ 5: round up | < 5: round down
Round 7,349 to nearest hundred: look at tens digit (4 < 5) → 7,300
Be My Multiple, I'll be Your Factor
Class 5HCF × LCM Relationship
HCF × LCM = Product of two numbers
For 12 and 18: HCF=6, LCM=36. Check: 6×36 = 216 = 12×18 ✓
Be My Multiple, I'll be Your Factor
Class 5Finding HCF (Division Method)
Divide larger by smaller; replace larger with remainder; repeat till remainder = 0
HCF(18,12): 18÷12=1 R6; 12÷6=2 R0; HCF=6
Can You See the Pattern?
Class 5Fibonacci Rule
F(n) = F(n-1) + F(n-2)
Starting values: F(1)=1, F(2)=1
Can You See the Pattern?
Class 5Magic Sum Formula
Magic sum of n×n square using 1 to n² = n(n²+1)/2
3×3 square: 3×(9+1)/2 = 3×5 = 15
Mapping Your Way
Class 5Speed-Distance-Time Triangle
S = D/T | D = S×T | T = D/S
Speed = 60 km/h, Time = 2.5 h → Distance = 60×2.5 = 150 km
Boxes and Sketches
Class 5Volume of Cuboid
V = l × b × h
4 cm × 3 cm × 5 cm = 60 cm³
Boxes and Sketches
Class 5Volume of Cube
V = s³
6 cm cube: V = 6³ = 216 cm³
Boxes and Sketches
Class 5Surface Area of Cube
SA = 6s²
5 cm cube: SA = 6×25 = 150 cm²
Tenths and Hundredths
Class 5Decimal to Fraction
Move denominator as power of 10 based on decimal places
0.7 = 7/10; 0.45 = 45/100; 0.125 = 125/1000
Tenths and Hundredths
Class 5Comparing Decimals
Compare whole part first; if equal compare tenth; if equal compare hundredth
3.45 vs 3.52: whole equal; tenths 4<5; so 3.45 < 3.52
Area and its Boundary
Class 5Area of Rectangle
A = l × b
l=length, b=breadth
Area and its Boundary
Class 5Area of Square
A = s²
s=side
Area and its Boundary
Class 5Perimeter of Rectangle
P = 2(l + b)
l=12cm, b=7cm: P=2×(12+7)=2×19=38 cm
Knowing Our Numbers
Class 6Place Value
Place Value = Face Value × Position Value
Position values: 1, 10, 100, 1000...
Knowing Our Numbers
Class 6Estimation (nearest 10)
If units ≥ 5: add 10, units=0. If units < 5: units=0
67 → 70, 54 → 50, 85 → 90
Knowing Our Numbers
Class 6Large Number Formula
1 crore = 100 lakhs = 10 million
2.5 crore = 25 million = 25,000,000
Playing with Numbers
Class 6HCF × LCM Relation
HCF(a,b) × LCM(a,b) = a × b
HCF(4,6)=2, LCM(4,6)=12. Check: 2×12=24=4×6 ✓
Playing with Numbers
Class 6Divisibility by 3
Sum of all digits divisible by 3
783: 7+8+3=18, 18÷3=6. So 783 is divisible by 3 ✓
Playing with Numbers
Class 6Divisibility by 9
Sum of all digits divisible by 9
5832: 5+8+3+2=18, 18÷9=2. So 5832 divisible by 9 ✓
Whole Numbers
Class 6Commutative Property
a + b = b + a | a × b = b × a
7+3=3+7=10, 4×6=6×4=24
Whole Numbers
Class 6Associative Property
(a+b)+c = a+(b+c) | (a×b)×c = a×(b×c)
(2+3)+4 = 2+(3+4) = 9
Whole Numbers
Class 6Distributive Property
a × (b + c) = a×b + a×c
Most useful property for mental math
Understanding Elementary Shapes
Class 6Complementary Angles
a + b = 90° (they complement each other)
Complement of 35° = 90-35 = 55°
Understanding Elementary Shapes
Class 6Supplementary Angles
a + b = 180° (they supplement each other)
Supplement of 110° = 180-110 = 70°
Understanding Elementary Shapes
Class 6Euler's Formula for 3D shapes
Faces + Vertices - Edges = 2
Cube: 6+8-12=2 ✓, Tetrahedron: 4+4-6=2 ✓
Basic Geometrical Ideas
Class 6Sum of angles in triangle
∠A + ∠B + ∠C = 180°
If two angles are 60° and 70°, third angle = 180-60-70 = 50°
Basic Geometrical Ideas
Class 6Sum of angles in quadrilateral
∠A + ∠B + ∠C + ∠D = 360°
If three angles are 90°, 90°, 100°: fourth = 360-280 = 80°
Basic Geometrical Ideas
Class 6Diameter and Radius
d = 2r | r = d/2
r=5cm → d=10cm. d=14cm → r=7cm
Algebra
Class 6Matchstick Pattern (triangles)
n triangles require (2n+1) matchsticks
4 triangles: 2×4+1 = 9 matchsticks
Algebra
Class 6Perimeter using variable
Square with side l: Perimeter = 4l
l=5cm: P=4×5=20cm. l=x cm: P=4x cm
Decimals
Class 6Decimal Place Values
...Hundreds | Tens | Ones . Tenths | Hundredths | Thousandths...
5.374: 5 = ones, 3 = tenths, 7 = hundredths, 4 = thousandths
Decimals
Class 6Fraction to Decimal
Divide numerator by denominator
3/4 = 3÷4 = 0.75. 1/8 = 0.125. 1/3 = 0.333...
Decimals
Class 6Money Conversion
₹1 = 100 paise. So ₹p.q means p rupees q paise
₹7.05 = 7 rupees 5 paise = 705 paise
Integers
Class 6Additive Inverse
a + (-a) = 0, so additive inverse of a is -a
Additive inverse of 7 is -7. Of -12 is 12. Of 0 is 0.
Integers
Class 6Integer Subtraction
a - b = a + (-b)
5 - (-3) = 5 + 3 = 8. (-4) - (-7) = (-4) + 7 = 3
Integers
Class 6Sign Rules for Addition
+×+ = +, -×- = +, +×- = -, -×+ = -
(+7)×(+3)=+21, (-7)×(-3)=+21, (+7)×(-3)=-21
Data Handling
Class 6Mean (Average)
Mean = Sum of all values / Number of values
Data: 12, 18, 15, 20, 10. Sum=75, n=5. Mean=75/5=15
Data Handling
Class 6Tally Marks
Every 5th mark crosses previous 4 (like a gate)
HH HH HH | = 11 items
Fractions
Class 6Equivalent Fractions
a/b = (a×n)/(b×n) for any n≠0
2/3 = 4/6 = 6/9 = 10/15
Fractions
Class 6Converting Mixed to Improper
a(b/c) = (a×c + b)/c
2¾ = (2×4+3)/4 = 11/4
Fractions
Class 6Adding Fractions (different denom)
a/b + c/d = (ad+bc)/bd
1/3 + 1/4 = (4+3)/12 = 7/12
Mensuration
Class 6Perimeter of Rectangle
P = 2(l + b)
l=length, b=breadth
Mensuration
Class 6Perimeter of Square
P = 4 × s
s=side length
Mensuration
Class 6Area of Rectangle
A = l × b
l=8cm, b=5cm → A=8×5=40 cm²
Mensuration
Class 6Area of Square
A = s × s = s²
Side=7cm → A=7²=49 cm²
Ratio and Proportion
Class 6Ratio in simplest form
a:b = a/HCF(a,b) : b/HCF(a,b)
24:36 → HCF=12 → 2:3
Ratio and Proportion
Class 6Proportion Test
a:b::c:d if and only if a×d = b×c
3:4::6:8 → 3×8=24, 4×6=24 ✓ In proportion
Symmetry
Class 6Lines of symmetry
Regular polygon with n sides has n lines of symmetry
Equilateral triangle (n=3): 3 lines. Square (n=4): 4 lines. Regular hexagon (n=6): 6 lines
Lines and Angles
Class 7Complementary angles: a + b = 90°
Complementary angles: a + b = 90°
Lines and Angles
Class 7Supplementary angles: a + b = 180°
Supplementary angles: a + b = 180°
Lines and Angles
Class 7Vertically opposite angles are equal
Vertically opposite angles are equal
Exponents and Powers
Class 7aᵐ × aⁿ = aᵐ⁺ⁿ
aᵐ × aⁿ = aᵐ⁺ⁿ
Exponents and Powers
Class 7aᵐ ÷ aⁿ = aᵐ⁻ⁿ
aᵐ ÷ aⁿ = aᵐ⁻ⁿ
Exponents and Powers
Class 7(aᵐ)ⁿ = aᵐⁿ
(aᵐ)ⁿ = aᵐⁿ
Exponents and Powers
Class 7a⁰ = 1
a⁰ = 1
Integers
Class 7Sign Rules
(+)×(+)=+, (−)×(−)=+, (+)×(−)=−, (−)×(+)=-
(−5)×(+3)=−15, (−4)×(−7)=+28
Integers
Class 7Absolute Value
|a| = a if a≥0, |a| = −a if a<0
|−8|=8, |+6|=6, |0|=0
Data Handling
Class 7Mean
Mean = Sum of all observations / Total number
Data: 4,7,8,9,2. Sum=30, n=5. Mean=6
Data Handling
Class 7Probability
P(event) = Number of favourable outcomes / Total outcomes
P(head) = 1/2. P(ace from deck) = 4/52 = 1/13
Perimeter and Area
Class 7Area of Triangle
A = ½ × b × h
h is perpendicular height, not slant
Perimeter and Area
Class 7Area of Parallelogram
A = b × h
b=8cm, h=5cm: A = 8×5 = 40 cm²
Perimeter and Area
Class 7Circumference of Circle
C = 2πr = πd
r=7cm: C = 2×22/7×7 = 44 cm
Perimeter and Area
Class 7Area of Circle
A = πr²
r=7cm: A = 22/7×49 = 154 cm²
Perimeter and Area
Class 7Area of Semi-circle
A = πr²/2
r=7: A = 154/2 = 77 cm²
Fractions and Decimals
Class 7Fraction multiplication
a/b × c/d = ac/bd
2/3 × 3/4 = 6/12 = 1/2
Fractions and Decimals
Class 7Fraction division (reciprocal)
a/b ÷ c/d = a/b × d/c
2/3 ÷ 4/5 = 2/3 × 5/4 = 10/12 = 5/6
Simple Equations
Class 7Linear Equation
ax + b = c → x = (c - b) / a
a ≠ 0
Simple Equations
Class 7Transposition Rule
If ax + b = c, then ax = c - b (b moves to RHS with -ve sign)
2x + 7 = 15 → 2x = 15-7 = 8 → x = 4
Simple Equations
Class 7Check Solution
Substitute x back in original equation → LHS must equal RHS
x=5 in 3x+4=19: 3(5)+4=15+4=19 ✓
Triangles and Its Properties
Class 7Angle sum in triangle
∠A + ∠B + ∠C = 180°
Angles 50°, 70°: third = 180-120 = 60°
Triangles and Its Properties
Class 7Exterior angle theorem
Exterior angle = sum of opposite interior angles
Interior angles 65° and 75°: exterior angle = 65+75 = 140°
Triangles and Its Properties
Class 7Pythagoras theorem
c² = a² + b²
c is hypotenuse (opposite to right angle)
Comparing Quantities
Class 7Percentage
x% of y = (x/100) × y
Very commonly used in daily life
Comparing Quantities
Class 7Profit %
Profit% = (Profit / CP) × 100 = (SP-CP)/CP × 100
CP=₹200, SP=₹250: Profit=₹50, Profit%=50/200×100=25%
Comparing Quantities
Class 7Loss %
Loss% = (Loss / CP) × 100
CP=₹500, SP=₹400: Loss=₹100, Loss%=20%
Comparing Quantities
Class 7Simple Interest
SI = P × R × T / 100
Amount = P + SI
Comparing Quantities
Class 7Find SP from Profit%
SP = CP × (100 + Profit%) / 100
CP=₹800, Profit%=25: SP=800×125/100=₹1000
Rational Numbers
Class 7a/b where b ≠ 0
a/b where b ≠ 0
Rational Numbers
Class 7a/b = ac/bc
a/b = ac/bc
Visualising Solid Shapes
Class 7Euler's formula: F + V - E = 2
Euler's formula: F + V - E = 2
Data Handling
Class 8P(E) = Favourable outcomes / Total outcomes
P(E) = Favourable outcomes / Total outcomes
Exponents and Powers
Class 8a⁻ⁿ = 1/aⁿ
a⁻ⁿ = 1/aⁿ
Exponents and Powers
Class 8aᵐ × aⁿ = aᵐ⁺ⁿ
aᵐ × aⁿ = aᵐ⁺ⁿ
Exponents and Powers
Class 8aᵐ/aⁿ = aᵐ⁻ⁿ
aᵐ/aⁿ = aᵐ⁻ⁿ
Exponents and Powers
Class 8(aᵐ)ⁿ = aᵐⁿ
(aᵐ)ⁿ = aᵐⁿ
Linear Equations in One Variable
Class 8Consecutive integers formula
n, n+1, n+2 (consecutive). n, n+2, n+4 (consecutive odd/even)
Sum of 4 consecutive integers = 4n+6. If =54: n=12, so 12,13,14,15
Rational Numbers
Class 8Standard Form of Rational Number
p/q where HCF(p,q)=1 and q>0
-6/4 in standard form: divide by HCF(6,4)=2 → -3/2
Rational Numbers
Class 8Multiplicative Inverse
Reciprocal of p/q = q/p
Reciprocal of 3/7 = 7/3. Reciprocal of -5/8 = -8/5
Comparing Quantities
Class 8Discount
SP = MP - Discount = MP × (100-Discount%)/100
MP=₹800, Disc=25%: SP=800×75/100=₹600
Comparing Quantities
Class 8GST Calculation
Amount paid = SP + (GST% × SP)/100 = SP×(100+GST%)/100
SP=₹2000, GST=18%: Amount=2000×118/100=₹2360
Comparing Quantities
Class 8Compound Interest
A = P(1 + R/100)ⁿ | CI = A - P
n = number of years (or periods)
Comparing Quantities
Class 8SI vs CI Difference
CI - SI = P(R/100)² (for 2 years)
P=₹5000, R=10%: CI-SI=5000×0.01=₹50
Mensuration
Class 8Area of Trapezium
A = ½ × (a + b) × h
a,b are parallel sides; h is perpendicular height
Mensuration
Class 8Cuboid TSA
TSA = 2(lb + bh + lh)
l=5, b=3, h=4: TSA=2(15+12+20)=94 cm²
Mensuration
Class 8Cuboid Volume
V = l × b × h
l=5, b=3, h=4: V=60 cm³
Mensuration
Class 8Cylinder CSA
CSA = 2πrh
r=7, h=10: CSA=2×22/7×7×10=440 cm²
Mensuration
Class 8Cylinder Volume
V = πr²h
1000 cm³ = 1 litre
Factorisation
Class 8a²-b² = (a+b)(a-b)
a²-b² = (a+b)(a-b)
Factorisation
Class 8a²+2ab+b² = (a+b)²
a²+2ab+b² = (a+b)²
Cubes and Cube Roots
Class 8Cube of a number
n³ = n × n × n
5³=125, 10³=1000, (-3)³=-27
Cubes and Cube Roots
Class 8Cube root
∛n = m means m³ = n
∛125=5 because 5³=125. ∛(-125)=-5
Algebraic Expressions and Identities
Class 8(a+b)² Identity
(a+b)^2 = a^2 + 2ab + b^2
(x+5)² = x²+10x+25. (2+3)²=4+12+9=25=5² ✓
Algebraic Expressions and Identities
Class 8(a-b)² Identity
(a-b)^2 = a^2 - 2ab + b^2
(x-4)² = x²-8x+16
Algebraic Expressions and Identities
Class 8Difference of squares
(a+b)(a-b) = a^2 - b^2
(x+7)(x-7)=x²-49. 103×97=(100)²-3²=9991
Direct and Inverse Proportions
Class 8Direct: x/y = k (constant)
Direct: x/y = k (constant)
Direct and Inverse Proportions
Class 8Inverse: x × y = k
Inverse: x × y = k
Squares and Square Roots
Class 8√(a × b) = √a × √b
√(a × b) = √a × √b
Squares and Square Roots
Class 8(a+b)² = a²+2ab+b²
(a+b)² = a²+2ab+b²
Squares and Square Roots
Class 8(a-b)² = a²-2ab+b²
(a-b)² = a²-2ab+b²
Understanding Quadrilaterals
Class 8Sum of angles of quadrilateral = 360°
Sum of angles of quadrilateral = 360°
Understanding Quadrilaterals
Class 8Opposite angles of parallelogram are equal
Opposite angles of parallelogram are equal
Visualising Solid Shapes
Class 8Euler's formula: F + V - E = 2
Euler's formula: F + V - E = 2
Areas of Parallelograms and Triangles
Class 9Area = base × height
Area = base × height
Areas of Parallelograms and Triangles
Class 9Area of triangle = ½ × b × h
Area of triangle = ½ × b × h
Heron's Formula
Class 9s = (a+b+c)/2
s = (a+b+c)/2
Heron's Formula
Class 9Area = √[s(s-a)(s-b)(s-c)]
Area = √[s(s-a)(s-b)(s-c)]
Linear Equations in Two Variables
Class 9ax + by + c = 0
ax + by + c = 0
Lines and Angles
Class 9Angle sum = 180°
Angle sum = 180°
Lines and Angles
Class 9Vertically opposite angles are equal
Vertically opposite angles are equal
Number Systems
Class 9Rationalising Factor
Multiply by conjugate: (a+√b)(a-√b) = a²-b
Rationalise 1/(√2+1): multiply by (√2-1)/(√2-1) = (√2-1)/(2-1) = √2-1
Number Systems
Class 9Laws of Exponents
aᵐ × aⁿ = aᵐ⁺ⁿ | aᵐ/aⁿ = aᵐ⁻ⁿ | (aᵐ)ⁿ = aᵐⁿ
2³ × 2⁴ = 2⁷ = 128 | 3⁵/3² = 3³ = 27
Number Systems
Class 9nth Root
a^(1/n) = ⁿ√a | a^(m/n) = ⁿ√(aᵐ)
8^(1/3) = ∛8 = 2 | 27^(2/3) = (∛27)² = 3² = 9
Polynomials
Class 9Key Identities
(a+b)² = a²+2ab+b²
(a-b)² = a²-2ab+b²
(a+b)(a-b) = a²-b²
(x+3)² = x²+6x+9 | (2x-5)(2x+5) = 4x²-25
Polynomials
Class 9Cubic Identities
(a+b)³ = a³+3a²b+3ab²+b³
(a-b)³ = a³-3a²b+3ab²-b³
a³+b³ = (a+b)(a²-ab+b²)
a³-b³ = (a-b)(a²+ab+b²)
(x+2)³ = x³+6x²+12x+8
Polynomials
Class 9Special: a³+b³+c³
If a+b+c=0, then a³+b³+c³ = 3abc
If x+y+z=0, then x³+y³+z³ = 3xyz
Probability
Class 9P(E) = n(favorable outcomes)/n(total outcomes)
P(E) = n(favorable outcomes)/n(total outcomes)
Statistics
Class 9Mean = Σx/n
Mean = Σx/n
Statistics
Class 9Mode = most frequent value
Mode = most frequent value
Surface Areas and Volumes
Class 9Cylinder
CSA=2πrh | TSA=2πr(r+h) | V=πr²h
π ≈ 22/7 ≈ 3.14159
Surface Areas and Volumes
Class 9Cone
l=√(r²+h²) | CSA=πrl | TSA=πr(r+l) | V=⅓πr²h
r=3, h=4: l=5, V=⅓×π×9×4≈37.7 cm³
Surface Areas and Volumes
Class 9Sphere
SA=4πr² | V=4/3 πr³
r=6cm: SA=4π×36≈452.4 cm² | V=4/3×π×216≈904.8 cm³
Surface Areas and Volumes
Class 9Hemisphere
CSA=2πr² | TSA=3πr² | V=2/3 πr³
r=7: TSA=3×22/7×49=462 cm²
Science
58 formulasAcids, Bases and Salts
Class 10pH < 7 = acid
pH < 7 = acid
Acids, Bases and Salts
Class 10pH > 7 = base
pH > 7 = base
Acids, Bases and Salts
Class 10pH = 7 = neutral
pH = 7 = neutral
Electricity
Class 10Ohm's Law
V = IR (V=voltage, I=current, R=resistance)
V=12V, R=4Ω: I=V/R=12/4=3A
Electricity
Class 10Series Resistance
R_total = R₁ + R₂ + R₃
3Ω + 5Ω + 2Ω = 10Ω
Electricity
Class 10Parallel Resistance
1/R_eq = 1/R₁ + 1/R₂ + 1/R₃
6Ω and 3Ω in parallel: 1/R=1/6+1/3=1/2 → R=2Ω
Electricity
Class 10Electrical Power
P = VI = I²R = V²/R
I=2A, R=5Ω: P=I²R=4×5=20W
Electricity
Class 10Electrical Energy
E = P × t = VIt
1000W heater for 2 hours: E=1000×7200=7,200,000 J = 2 kWh
Electricity
Class 10Heating Effect (Joule)
H = I²Rt
I=3A, R=10Ω, t=60s: H=9×10×60=5400 J
Light — Reflection and Refraction
Class 101/v + 1/u = 1/f
1/v + 1/u = 1/f
Light — Reflection and Refraction
Class 10m = -v/u
m = -v/u
Light — Reflection and Refraction
Class 10n = sin i/sin r
n = sin i/sin r
Light — Reflection and Refraction
Class 10P = 1/f (in metres)
P = 1/f (in metres)
Components of Food
Class 6Iodine Test for Starch
Food + Iodine solution → Blue-black colour = starch present
Rice: blue-black (starch present). Onion: no colour change (no starch)
Motion and Measurement of Distances
Class 6Unit Conversions
1 km = 1000 m = 100,000 cm = 10,00,000 mm
Your height 160cm = 1.6m = 0.0016km
Motion and Measurement of Distances
Class 6Time
1 hour = 60 minutes = 3600 seconds
2.5 hours = 150 minutes = 9000 seconds
Getting to Know Plants
Class 6Photosynthesis Equation
CO₂ + H₂O + Sunlight → Glucose + O₂
Chlorophyll in leaves captures sunlight energy
Light, Shadows and Reflections
Class 6Law of Reflection
Angle of incidence = Angle of reflection
Light hits mirror at 40° → reflects at 40° (both measured from normal)
Heat
Class 7Temperature Conversion
F = (9/5)C + 32 | C = (F-32) × 5/9
Normal body temperature
Heat
Class 7Kelvin to Celsius
K = C + 273
0°C = 273K (freezing of water). -273°C = 0K (absolute zero)
Acids, Bases and Salts
Class 7Neutralisation
Acid + Base → Salt + Water
HCl + NaOH → NaCl + H₂O (table salt + water)
Acids, Bases and Salts
Class 7pH Scale
pH 0-6: acid (lower = stronger). pH 7: neutral. pH 8-14: base (higher = stronger)
Battery acid: pH 1. Lemon: pH 2. Blood: pH 7.4. Baking soda: pH 9. Drain cleaner: pH 14
Respiration in Organisms
Class 7Glucose + Oxygen → CO₂ + Water + Energy
Glucose + Oxygen → CO₂ + Water + Energy
Respiration in Organisms
Class 7C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + Energy
Nutrition in Plants
Class 7Photosynthesis Equation
6CO₂ + 6H₂O + light → C₆H₁₂O₆ + 6O₂
Occurs in chloroplasts of leaf cells
Physical and Chemical Changes
Class 7Rusting (simplified)
Iron + Oxygen + Water → Iron Oxide (rust)
4Fe + 3O₂ + 6H₂O → 4Fe(OH)₃ → Fe₂O₃ (rust)
Motion and Time
Class 7Speed
Speed = Distance / Time
SI unit is m/s
Motion and Time
Class 7Unit Conversion
1 km/h = 5/18 m/s | 1 m/s = 18/5 km/h = 3.6 km/h
72 km/h = 72×5/18 = 20 m/s
Motion and Time
Class 7Pendulum Time Period
T = 2π√(L/g)
T depends only on length L, not mass
Motion and Time
Class 7Distance from Graph
Distance = Speed × Time = Area under speed-time graph
Speed=40m/s for 5s: Distance=40×5=200m
Microorganisms: Friend and Foe
Class 8Pasteurization Temperature
Milk heated to 70°C for 15 seconds OR 63°C for 30 minutes
Developed by Louis Pasteur in 1864
Metals and Non-metals
Class 8Reactivity Series (decreasing)
K > Na > Ca > Mg > Al > Zn > Fe > Pb > H > Cu > Ag > Au
More reactive metal displaces less reactive from solution
Light
Class 8Law of Reflection
Angle of incidence (i) = Angle of reflection (r)
Light hits mirror at 35°: reflects at 35°
Light
Class 8Speed and Refractive Index
n = c/v (refractive index = speed in vacuum / speed in medium)
Glass n≈1.5: light slows to c/1.5 = 2×10⁸ m/s
Combustion and Flame
Class 8Calorific value = Energy released per kg of fuel
Calorific value = Energy released per kg of fuel
Force and Pressure
Class 8Pressure = Force / Area
Pressure = Force / Area
Force and Pressure
Class 8P = F/A
P = F/A
Sound
Class 8Speed of Sound
Speed = Distance / Time (like all speed)
Speed varies with temperature and medium
Sound
Class 8Echo Minimum Distance
Minimum distance = (Speed of sound × 0.1s) / 2 = 17.15 m
Human ear cannot distinguish sounds less than 0.1s apart
Sound
Class 8Frequency and Pitch
Higher frequency → Higher pitch (shriller sound)
Whistle: ~3000 Hz (high pitch). Bass drum: ~50-100 Hz (low pitch)
Atoms and Molecules
Class 9Law of conservation of mass
Law of conservation of mass
Atoms and Molecules
Class 9Law of constant proportions
Law of constant proportions
Gravitation
Class 9F = Gm₁m₂/r²
F = Gm₁m₂/r²
Gravitation
Class 9g = GM/R²
g = GM/R²
Gravitation
Class 9W = mg
W = mg
Motion
Class 9Speed
v = d/t
Car travels 120 km in 2h: v = 120/2 = 60 km/h
Motion
Class 91st Equation of Motion
v = u + at
u=initial velocity, v=final velocity, a=acceleration, t=time
Motion
Class 92nd Equation of Motion
s = ut + ½at²
u=0, a=10, t=5: s=0+½×10×25=125m
Motion
Class 93rd Equation of Motion
v² = u² + 2as
u=0, a=10, s=20: v²=400, v=20m/s
Motion
Class 9Average Velocity (uniform acc)
v_avg = (u+v)/2
u=10, v=30: avg=20 m/s
Force and Laws of Motion
Class 9Newton's Second Law
F = ma = Δp/Δt
F in Newtons, m in kg, a in m/s²
Force and Laws of Motion
Class 9Momentum
p = mv
Truck: 5000kg×20m/s = 100,000 kg⋅m/s | Ball: 0.1kg×30m/s = 3 kg⋅m/s
Force and Laws of Motion
Class 9Impulse
Impulse = F × t = Δp = m(v-u)
Bat hits ball: F=500N for 0.02s → Impulse=10 N⋅s
Force and Laws of Motion
Class 9Conservation of Momentum
m₁u₁ + m₂u₂ = m₁v₁ + m₂v₂
2kg at 5m/s hits 3kg at rest: 10=2v₁+3v₂. If stick: v=(10)/5=2 m/s
Work and Energy
Class 9W = F × s
W = F × s
Work and Energy
Class 9KE = ½mv²
KE = ½mv²
Work and Energy
Class 9PE = mgh
PE = mgh
Work and Energy
Class 9P = W/t
P = W/t
Physics
61 formulasGravitation
Class 11Universal Gravitation
F = Gm₁m₂/r²
G = 6.674×10⁻¹¹ N⋅m²/kg²
Gravitation
Class 11g at surface
g = GM/R²
M=6×10²⁴kg, R=6.4×10⁶m: g=6.67×10⁻¹¹×6×10²⁴/(6.4×10⁶)² ≈ 9.8 m/s²
Gravitation
Class 11g at height h
g_h = g(R/(R+h))² ≈ g(1-2h/R) for h<<R
At h=R: g_h = g/4. At h=2R: g_h = g/9
Gravitation
Class 11Orbital Velocity
v_o = √(GM/r) = √(gR²/r)
Near Earth surface (r≈R): v_o = √(9.8×6.4×10⁶) ≈ 7920 m/s ≈ 7.9 km/s
Gravitation
Class 11Escape Velocity
v_e = √(2GM/R) = √(2gR) = √2 × v_o
v_e = √(2×9.8×6.4×10⁶) ≈ 11,200 m/s ≈ 11.2 km/s
Gravitation
Class 11Kepler's 3rd Law
T² ∝ r³ → T₁²/T₂² = r₁³/r₂³
Earth: T=1yr, r=1AU. Mars: r=1.52AU → T²=1.52³=3.51 → T=1.88 years
Laws of Motion
Class 11F = ma
F = ma
Laws of Motion
Class 11p = mv
p = mv
Laws of Motion
Class 11Impulse = Δp
Impulse = Δp
Motion in a Plane
Class 11Range = u²sin2θ/g
Range = u²sin2θ/g
Motion in a Plane
Class 11Maximum height = u²sin²θ/2g
Maximum height = u²sin²θ/2g
Motion in a Plane
Class 11Time of flight = 2usinθ/g
Time of flight = 2usinθ/g
Motion in a Straight Line
Class 111st Equation of Motion
v = u + at
u=initial velocity, v=final velocity
Motion in a Straight Line
Class 112nd Equation of Motion
s = ut + ½at²
u=0, a=10, t=3: s=0+½×10×9=45 m
Motion in a Straight Line
Class 113rd Equation of Motion
v² = u² + 2as
u=0, a=10, s=20: v²=400, v=20 m/s
Motion in a Straight Line
Class 11Distance in nth second
sₙ = u + a(2n-1)/2
Distance in the nth second (not total)
Motion in a Straight Line
Class 11Average Velocity
v_avg = (u+v)/2 [only for uniform acceleration]
u=10, v=30: avg=20 m/s
Oscillations
Class 11T = 2π√(l/g)
T = 2π√(l/g)
Oscillations
Class 11T = 2π√(m/k)
T = 2π√(m/k)
System of Particles and Rotational Motion
Class 11τ = r×F
τ = r×F
System of Particles and Rotational Motion
Class 11L = Iω
L = Iω
System of Particles and Rotational Motion
Class 11τ = Iα
τ = Iα
Waves
Class 11v = fλ
v = fλ
Waves
Class 11v = √(T/μ)
v = √(T/μ)
Work, Energy and Power
Class 11W = F·d·cosθ
W = F·d·cosθ
Work, Energy and Power
Class 11KE = ½mv²
KE = ½mv²
Work, Energy and Power
Class 11P = W/t
P = W/t
Alternating Current
Class 12Vrms = V₀/√2
Vrms = V₀/√2
Alternating Current
Class 12Z = √(R²+X²)
Z = √(R²+X²)
Alternating Current
Class 12P = VrmsIrms cosφ
P = VrmsIrms cosφ
Atoms
Class 12rn = 0.529n² Å
rn = 0.529n² Å
Atoms
Class 12En = -13.6/n² eV
En = -13.6/n² eV
Current Electricity
Class 12I = nAvde
I = nAvde
Current Electricity
Class 12R = ρl/A
R = ρl/A
Current Electricity
Class 12Kirchhoff: ΣI=0, ΣV=0
Kirchhoff: ΣI=0, ΣV=0
Dual Nature of Radiation and Matter
Class 12E = hν
E = hν
Dual Nature of Radiation and Matter
Class 12KEmax = hν - W₀
KEmax = hν - W₀
Dual Nature of Radiation and Matter
Class 12λ = h/mv
λ = h/mv
Electric Charges and Fields
Class 12Coulomb's Law
F = kq₁q₂/r² = q₁q₂/(4πε₀r²)
k = 9×10⁹ N⋅m²/C²
Electric Charges and Fields
Class 12Electric Field
E = F/q₀ = kq/r² (point charge)
q₀ is positive test charge
Electric Charges and Fields
Class 12Gauss's Law
φ = ∮E⃗⋅dA⃗ = Q_enc/ε₀
Charge Q inside sphere of any radius: φ = Q/ε₀ (same for any closed surface!)
Electric Charges and Fields
Class 12Field due to Line Charge
E = λ/(2πε₀r)
λ=1μC/m, r=0.1m: E=10⁻⁶/(2π×8.85×10⁻¹²×0.1)=1.8×10⁵ N/C
Electromagnetic Induction
Class 12EMF = -dΦ/dt
EMF = -dΦ/dt
Electromagnetic Induction
Class 12EMF = Blv
EMF = Blv
Electromagnetic Induction
Class 12L = NΦ/I
L = NΦ/I
Electrostatic Potential and Capacitance
Class 12V = kq/r
V = kq/r
Electrostatic Potential and Capacitance
Class 12C = Q/V
C = Q/V
Electrostatic Potential and Capacitance
Class 12U = ½CV²
U = ½CV²
Electrostatic Potential and Capacitance
Class 12Series: 1/C = 1/C₁+1/C₂
Series: 1/C = 1/C₁+1/C₂
Moving Charges and Magnetism
Class 12F = qv×B
F = qv×B
Moving Charges and Magnetism
Class 12B = μ₀I/2πr (wire)
B = μ₀I/2πr (wire)
Moving Charges and Magnetism
Class 12B = μ₀nI (solenoid)
B = μ₀nI (solenoid)
Nuclei
Class 12E = mc²
E = mc²
Nuclei
Class 12ΔE = Δm × c²
ΔE = Δm × c²
Ray Optics
Class 12Mirror: 1/v+1/u=1/f
Mirror: 1/v+1/u=1/f
Ray Optics
Class 12Lens: 1/v-1/u=1/f
Lens: 1/v-1/u=1/f
Ray Optics
Class 12n = sin i/sin r
n = sin i/sin r
Wave Optics
Class 12YDSE Fringe Width
β = λD/d
β = distance between consecutive bright (or dark) fringes
Wave Optics
Class 12Path Difference
Bright: Δ=nλ (n=0,±1,±2...) | Dark: Δ=(2n+1)λ/2
For 3rd bright fringe: Δ=3λ. For 2nd dark: Δ=3λ/2
Wave Optics
Class 12Intensity Pattern
I = 4I₀cos²(δ/2) where δ = phase difference = 2πΔ/λ
At bright fringe: δ=0,2π: I=4I₀ (maximum)
Wave Optics
Class 12Brewster's Law
tan(θ_B) = n (refractive index)
Glass n=1.5: θ_B=arctan(1.5)=56.3°
Chemistry
10 formulasEquilibrium
Class 11Equilibrium Constant
Kc = [C]^c[D]^d / [A]^a[B]^b
Only include aqueous and gaseous species; not pure solids/liquids
Equilibrium
Class 11Kp and Kc Relation
Kp = Kc(RT)^Δn
N₂+3H₂⇌2NH₃: Δn=2-4=-2, so Kp=Kc(RT)⁻²
Equilibrium
Class 11pH Definition
pH = -log[H⁺] | [H⁺][OH⁻] = 10⁻¹⁴ at 25°C
[H⁺]=10⁻³: pH=3 (acidic). [H⁺]=10⁻¹¹: pH=11 (basic)
Equilibrium
Class 11Henderson-Hasselbalch
pH = pKa + log([A⁻]/[HA])
Used for buffer pH calculation
Some Basic Concepts of Chemistry
Class 11n = m/M
n = m/M
Some Basic Concepts of Chemistry
Class 11Mole = 6.022×10²³ particles
Mole = 6.022×10²³ particles
Chemical Kinetics
Class 12Rate = k[A]ᵐ[B]ⁿ
Rate = k[A]ᵐ[B]ⁿ
Chemical Kinetics
Class 12k = Ae^(-Ea/RT)
k = Ae^(-Ea/RT)
Electrochemistry
Class 12ΔG° = -nFE°
ΔG° = -nFE°
Electrochemistry
Class 12E = E° - (RT/nF)lnQ
E = E° - (RT/nF)lnQ
Biology
3 formulasMolecular Basis of Inheritance
Class 12Chargaff's Rule
%A = %T | %G = %C | %A+%T+%G+%C = 100%
If A=30%: T=30%, G+C=40%, so G=C=20%
Molecular Basis of Inheritance
Class 12Number of Codons
4³ = 64 codons total. 61 sense + 3 stop codons
20 amino acids coded by 61 codons — most amino acids have multiple codons (degenerate code)
Molecular Basis of Inheritance
Class 12Replication time
Human DNA: ~3×10⁹ base pairs replicated in ~8 hours
Rate ≈ 100 base pairs/second at each replication fork
Accountancy
18 formulasBank Reconciliation Statement
Class 11Balance as per cash book ± Adjustments = Balance as per passbook
Balance as per cash book ± Adjustments = Balance as per passbook
Depreciation, Provisions and Reserves
Class 11SLM = (Cost - Residual Value) / Useful life
SLM = (Cost - Residual Value) / Useful life
Depreciation, Provisions and Reserves
Class 11WDV = Book value × Rate%
WDV = Book value × Rate%
Financial Statements — I
Class 11Gross Profit = Net Sales - Cost of goods sold
Gross Profit = Net Sales - Cost of goods sold
Financial Statements — I
Class 11Net Profit = Gross Profit - Indirect Expenses
Net Profit = Gross Profit - Indirect Expenses
Recording of Transactions — I
Class 11Assets = Liabilities + Capital
Assets = Liabilities + Capital
Recording of Transactions — I
Class 11Debit = Credit (in balanced accounts)
Debit = Credit (in balanced accounts)
Accounting for Partnership
Class 12P&L Appropriation = Net Profit - Interest on Capital - Salary + Interest on Drawings
P&L Appropriation = Net Profit - Interest on Capital - Salary + Interest on Drawings
Accounting for Share Capital
Class 12Securities Premium = Issue price - Face value
Securities Premium = Issue price - Face value
Accounting for Share Capital
Class 12Capital Reserve = Proceeds from re-issue of forfeited shares
Capital Reserve = Proceeds from re-issue of forfeited shares
Accounting Ratios
Class 12Current ratio = CA/CL
Current ratio = CA/CL
Accounting Ratios
Class 12Quick ratio = (CA-Inventory)/CL
Quick ratio = (CA-Inventory)/CL
Accounting Ratios
Class 12Gross profit ratio = GP/Net Sales × 100
Gross profit ratio = GP/Net Sales × 100
Accounting Ratios
Class 12Net profit ratio = NP/Net Sales × 100
Net profit ratio = NP/Net Sales × 100
Accounting Ratios
Class 12Return on equity = NP/Shareholders' equity × 100
Return on equity = NP/Shareholders' equity × 100
Dissolution of Partnership
Class 12Realisation account closes with profit/loss on realisation
Realisation account closes with profit/loss on realisation
Reconstitution of Partnership
Class 12Goodwill = Super profit × Years of purchase
Goodwill = Super profit × Years of purchase
Reconstitution of Partnership
Class 12Gaining ratio = New ratio - Old ratio
Gaining ratio = New ratio - Old ratio
Business Studies
3 formulasEconomics
22 formulasCorrelation
Class 11r = Σdx·dy / √(Σdx² × Σdy²)
r = Σdx·dy / √(Σdx² × Σdy²)
Measures of Central Tendency
Class 11Mean = ΣX/N
Mean = ΣX/N
Measures of Central Tendency
Class 11Median = L + (N/2 - CF)/f × h
Median = L + (N/2 - CF)/f × h
Measures of Dispersion
Class 11SD = √(Σfd²/N)
SD = √(Σfd²/N)
Measures of Dispersion
Class 11CV = (SD/Mean) × 100
CV = (SD/Mean) × 100
Determination of Income and Employment
Class 12Income = Consumption + Saving
Income = Consumption + Saving
Determination of Income and Employment
Class 12MPC = ΔC/ΔY
MPC = ΔC/ΔY
Determination of Income and Employment
Class 12MPS = ΔS/ΔY
MPS = ΔS/ΔY
Determination of Income and Employment
Class 12MPC + MPS = 1
MPC + MPS = 1
Determination of Income and Employment
Class 12Multiplier = 1/(1-MPC)
Multiplier = 1/(1-MPC)
Government Budget and the Economy
Class 12Fiscal deficit = Total expenditure - Revenue receipts - Non-debt capital receipts
Fiscal deficit = Total expenditure - Revenue receipts - Non-debt capital receipts
Government Budget and the Economy
Class 12Primary deficit = Fiscal deficit - Interest payments
Primary deficit = Fiscal deficit - Interest payments
National Income Accounting
Class 12GDP = C + I + G + (X-M)
GDP = C + I + G + (X-M)
National Income Accounting
Class 12NNP = GNP - Depreciation
NNP = GNP - Depreciation
National Income Accounting
Class 12National income = NNP - Indirect taxes + Subsidies
National income = NNP - Indirect taxes + Subsidies
Production and Costs
Class 12TC = TFC + TVC
TC = TFC + TVC
Production and Costs
Class 12MC = ΔTC/ΔQ
MC = ΔTC/ΔQ
Production and Costs
Class 12ATC = TC/Q
ATC = TC/Q
The Theory of the Firm Under Perfect Competition
Class 12Profit = TR - TC
Profit = TR - TC
The Theory of the Firm Under Perfect Competition
Class 12MR = MC (equilibrium)
MR = MC (equilibrium)
Theory of Consumer Behaviour
Class 12MUx/Px = MUy/Py (Cardinal)
MUx/Px = MUy/Py (Cardinal)
Theory of Consumer Behaviour
Class 12MRSxy = Px/Py (Ordinal)
MRSxy = Px/Py (Ordinal)