Answer
$y = \sqrt {10}$
Work Step by Step
In a $45^{\circ}-45^{\circ}-90^{\circ}$ triangle, we know that the hypotenuse is $\sqrt 2$ times each leg. Let's write an equation to solve for $y$, the length of the hypotenuse:
$y = \sqrt 2(\sqrt 5)$
Multiply:
$y = \sqrt {10}$
