Answer
5
Work Step by Step
Use Pythagorean theorem $a^{2}+b^{2}=c^{2}$ where $c$ is the length of the hypotenuse and $a$ and $b$ are the lengths of the two other sides.
$3^{2}+4^{2}=c^{2}
\\9 + 16 = c^{2}
\\25 = c^{2}$
Take the principal square root of both sides :
$\sqrt{25}=\sqrt{c^{2}}
\\5=c$
