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Sequences and Series · Class 11 · CBSE · Science Mathematics

The sum of the first n terms of a sequence is Sn = 3n² + 2n. What is the 10th term of the sequence?

Practice question from Sequences and Series (Class 11 · CBSE · Science Mathematics), with the correct answer and a step-by-step solution.

hard · MCQ · Q-2C10B6

The sum of the first n terms of a sequence is S_n = 3n² + 2n. What is the 10th term of the sequence?

  1. A.53
  2. B.57
  3. C.59Correct answer
  4. D.61

Solution

For any sequence, an=Sn−Sn−1a_n=S_n-S_{n-1}. Therefore, an=(3n2+2n)−[3(n−1)2+2(n−1)]=6n−1a_n=(3n²+2n)-[3(n-1)²+2(n-1)]=6n-1. Hence, a10=6(10)−1=59a_{10}=6(10)-1=59.

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