Question

What is the value of the geometric sequence for which a1=10 and r=0.5?

Answer 1

The formula for an infinite geometric sequence is the following:

$S_{∞}= \frac{a_{1}}{1-r}$

Just substitute the values of $a_{1}$ and r into the formula.

$S_{∞}=\frac{10}{1-0.5}$
$S_{∞}=\frac{10}{0.5}$
$S_{∞}= 20$

Therefore, the answer is 20.