Answer
$\dfrac{5}{3}$
Work Step by Step
Here, $a=1, r=\dfrac{2}{5}$; The common ratio is $|\dfrac{2}{5}| \lt 1$; so the series converges.
The sum of a geometric series can be found as:
$S=\dfrac{a}{1-r}=\dfrac{1}{1-\dfrac{2}{5}}=\dfrac{5}{3}$