Find the sum to indicated number of terms in each of the geometric progressions : 0.15, 0.015, 0.0015, . . . , 20 terms.

Explanation

In the given GP,

First-term, `a = 0.15`

Common ratio, `r = 0.1`

So, Sum of first 20 terms, `S_20 = (a(1-r^20))/(1-r)`

`S_20 = (0.15(1-(0.1)^20))/(1-0.1) = 0.15/0.9(1-(0.1)^20)`

`S_20 = 1/6(1-(0.1)^20)`