Question

For an arithmetic sequence where a1 = 13 and the common difference is 3, find s7.

A. 157
B. 151
C. 154
D. 162
10 points SHOW STEPS

Answer 1

Answer:

D ) 154

Explanation:

a 1 = 13, d = 3;

S n = n/2 * ( a 1 + a n )

a 7 = a 1 + 6 d = 13 + 3 * 6 = 13 + 18 = 31

S 7 = 7/2 * ( 13 + 31 ) = 7/2 * 44 = 154