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Class 10 · Mathematics (Basic) · Unit 5: Arithmetic Progressions

Selecting Terms Symmetrically

Lesson 4 of 6

For problems with sums of consecutive AP terms, take them symmetrically to simplify. Three terms:

a-d, a, a+d

. Four terms:

a-3d, a-d, a+d, a+3d

. Five terms:

a-2d, a-d, a, a+d, a+2d

. This makes the sum simply

ka

for

k

terms.

Sum of First n Terms

AP in Real Life

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