Question

Which series has a sum of 20?

Answer 1

Answer:

  see below

Step-by-step 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