The area of a right angled triangle is $240 cm^2$ and side other than hypotenuse is 30 cm , the perimeter of the triangle, is
A
20 cm
B
80 cm
C
100 cm
D
140 cm
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B
80 cm
(b) 80 cm Let the lengths of two sides, other than hypotenuse, of right triangle be $a cm$ and $b cm$. It is given that $a=30 cm$. Then, $\text { Area }=240 cm^2 \Rightarrow \frac{1}{2} a b=240 \Rightarrow 30 b=480 \Rightarrow b=16 cm$ Applying Pythagoras theorem, we obtain $\begin{aligned}& \text { Hypotenuse }=\sqrt{a^2+b^2}=\sqrt{30^2+16^2}=\sqrt{900+256}=\sqrt{1156} cm=34 cm \\ \therefore \quad & \text { Perimeter }=(30+16+34) cm=80 cm .\end{aligned}$
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