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The sum of the first n terms of an arithmetic progression is Sₙ = n² + 2n. What is its 10th term?

2456Medium DSSSB TGT Computer Science 0 replies 1 views
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The sum of the first n terms of an arithmetic progression is Sₙ = n² + 2n. What is its 10th term?

  • A21
  • B20
  • C22
  • D23
Correct answer: A

Explanation

The 10th term is S₁₀ − S₉ = (100 + 20) − (81 + 18) = 120 − 99 = 21.

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