How do you find the sum of the first 25 terms of the sequence: 7,19,31,43...?

1 Answer

37753775

Explanation:

The given series:

7, 19, 31, 43, \ldots

Above series is an arithmetic progression with a common difference

d=19-7=31-19=43-31=\ldots=12

First term: a=7

The sum of first n terms of an AP with term a & a common difference d is given as

S_n=n/2(2a+(n-1)d)

Hence, the sum of first n=25 terms of an AP with term a=7 & a common difference d=12 is given as

S_{25}=25/2(2\cdot 7+(25-1)12)

=3775