Question

if the sum of first 15 terms of the series 3+7+14+24+37+......... is 15k
,then k is equal to
a. 119
b. 126
c. 122
d. 81

Answer 1

From the difference table attached, the first 15 terms of this series are:

3, 7, 14, 24, 37, 53, 72, 94, 119, 147, 178, 212, 249, 289 and 332

The sum of these numbers = 15k, therefore;

3+ 7+ 14+ 24+ 37+ 53+ 72+ 94+ 119+ 147+ 178+ 212+ 249+ 289 +332 = 15k

1830 = 15k

k = 1830/15

k = 122

The correct answer is (C), 122