2021 · Q79
Suppose the nth term of a series is 1 + n/2 + n^2/2.. If there are 20 terms in the series, then the sum of the series is equal to
general-mental-abilityquantitative-aptitude
- A1360
- B1450
- C1500
- D1560
Explanation
The sum is Σ(1) + Σ(n/2) + Σ(n²/2) for n = 1 to 20. Σ(1) = 20; Σ(n/2) = (20 x 21/2)/2 = 105; Σ(n²/2) = (20 x 21 x 41/6)/2 = 1435. Adding them: 20 + 105 + 1435 = 1560. Hence option D is correct.