Question

What is the sum of the first five terms of a geometric series with a1=10 and r=1/5?

Answer 1

Sum of first `5` terms is `12.496`

Explanation:

First term `a1=10` , common ratio, `r=1/5=0.2`

number of terms , `n=5`

Sum of first `5` terms is `S_5=(a_1*(1-r^n))/(1-r)` or

`S_5=(10*(1-0.2^5))/(1-0.2)=12.496`

Sum of first `5` terms is `12.496` [Ans]