#### Answer

$\sqrt{11}\approx3.317 \text{ }ft$

#### Work Step by Step

Let the right triangle have $a$ and $b$ as the legs and $c$ as the hypotenuse. Using $a^2+b^2=c^2$ or the Pythagorean Theorem, with $
c=\sqrt{15}
$ and $
a=2
,$ then
\begin{array}{l}\require{cancel}
a^2+b^2=c^2
\\\\
2^2+b^2=(\sqrt{15})^2
\\\\
4+b^2=15
\\\\
b^2=15-4
\\\\
b^2=11
\\\\
b=\sqrt{11}
.\end{array}
Hence, the other leg is $
\sqrt{11}\approx3.317 \text{ }ft
$ long.