Question

Find the sum to indicated number of terms in each of the geometric progression. Exercise $7$ to $10$:
$0.15,0.015,0.0015,20terms$

Answer 1

Formula,

$S_n=\frac{a(1-r^n)}{1-r}$

Given,

$a=0.15$

$r=\frac{0.015}{0.15}=0.1$

$\therefore S_n=\frac{0.15(1-(0.1{)}^{20})}{1-0.1}$

$=\frac{0.15(1-(0.1{)}^{20})}{0.9}$

$=\frac{1-(0.1{)}^{20}}{6}$