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Mathematics (Maths Magic)Class 10Full Content

Arithmetic Progressions

Sequences with common difference, nth term and sum formulas.

Key Topics

Introduction

Open topic

An arithmetic progression is a list of numbers where the difference between consecutive terms stays constant. Such patterns appear in seating rows, savings plans and repeated schedules.

Arithmetic Progressions

Open topic

The first term is denoted by a and the common difference by d. Recognising whether a sequence is an AP is the first and most important step in this chapter.

nth Term of an AP

Open topic

The nth term helps us jump to any position in the progression without listing all terms. It is especially useful in board problems involving large term numbers.

Sum of First n Terms of an AP

Open topic

The sum formula compresses long repeated addition into a neat algebraic rule. Students should know both the general sum formula and the version using first and last term.

Summary

Open topic

By the end of the chapter, learners should be comfortable identifying APs, finding missing values, locating particular terms and summing terms quickly.

Formulas

aₙ = a + (n - 1)d
If a = 3 and d = 4, then a₅ = 3 + 4×4 = 19
Sum of First n Terms
Formula detail
Sₙ = n/2 [2a + (n - 1)d]
For a = 2, d = 3, n = 4: S₄ = 4/2[4 + 9] = 26
Sum Using Last Term
Formula detail
Sₙ = n/2 (a + l)
If first term is 5, last term is 25 and n = 5, sum = 75

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