Question

An Arithmetic series has 20 terms. The first term is -81. The sum of all the terms is -480. Use the arithmetic sum formula to find the last term

Answer 1

The last term is 33.

Explanation:

Sn = (n/2)(a1 + L) where a1 = first term and L = the last.

So:

-480 = (20/2) ( -81 + L)

-480 = 10( L - 81)

L- 81 = -480 / 10 = -48

L = -48 + 81

L = 33.