Question

what is the sum of the first 5 terms of a geometric series with a1=20 and r=1/4? express your answer as an improper fraction in lowest terms without using spaces.

Answer 1

\(\huge\color{ purple }{\huge {\bbox[5pt, yellow ,border:2px solid purple ]{ S_{n}=\frac{a_1(1-r^n)}{1-r} }}}\)

Answer 2

you are given the a_1, the number of terms, and the common ratio.