Question

Question 36

In a right angled $\Delta ABC$, if $\angle B={90}^{\circ }$, BC = 3 cm and AC = 5 cm, then the length of side AB is

a) 3 cm
b) 4 cm
c) 5 cm
d) 6 cm

Answer 1

Since, $\Delta ABC$ is a right angled triangle.

In right angled $\Delta ABC$,
$A{C}^2=A{B}^2+B{C}^2$ [by Pythagoras theorem]
$\Rightarrow 5^2=A{B}^2+3^2$ [$\because$ AC = 5 cm and BC = 3 cm, given]
$\Rightarrow A{B}^2=25-9\Rightarrow A{B}^2=16\Rightarrow AB=\sqrt{16}\Rightarrow AB=4cm$