Question

Which series has a sum of 20?

Answer 1

The answer is A) 5(3/4)^n-1.

Explanation:

Answer 2

see below

Explanation:

The sum of an infinite series with first term "a" and common ratio "r" is ...

S = a/(1 -r) . . . . . for |r| < 1

Then the sums for the given answer choices are ...

A: 5/(1 -3/4) = 20 . . . . . the answer of choice

B: 4/(1 -5/6) = 24

C: 4/(1 -1/5) = 5

D: 10/(1 -1/5) = 12.5