4. The shorter sides of a right-angled triangle have lengths $\sqrt{5}$ and $\sqrt{12}$. What is the length of the hypotenuse?
A $\sqrt{7}$
B $\sqrt{13}$
C $\sqrt{15}$
D $\sqrt{17}$
E 7
4. D Let the length of the hypotenuse of the triangle be $l$.
Then, by Pythagoras' Theorem, $l^{2}=(\sqrt{5})^{2}+(\sqrt{12})^{2}=5+12=17$.
So the length of the hypotenuse is $\sqrt{17}$.