Multiple choice general knowledge math & puzzles

find sum of 10 ten terms of series 1,8,15

  1. 215

  2. 315

  3. 325

  4. 335
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C Correct answer
Explanation

The series 1, 8, 15 is an arithmetic progression with common difference 7. Sum of n terms = n/2 × (2a + (n-1)d). For n=10: 10/2 × (2×1 + 9×7) = 5 × (2 + 63) = 5 × 65 = 325.

AI explanation

The series 1, 8, 15, ... is arithmetic with first term a=1 and common difference d=7. The sum of the first n terms is n/2 × (2a + (n-1)d); for n=10 this is 10/2 × (2 + 9×7) = 5 × 65 = 325.

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