Question

find first four terms of an arithmetic series if last term is 10 times first term and sum to n terms is 121

Answer 1

Answer: 120

Explanation:

S = n/2 (a(1) + a(n)), where n is the number of terms (10), a(1) is the first term (3), and a(n) is the last term (21).

By substitution, we have,

S = 10/2 (3 + 21)

S = 120