A circular wire of length 168 cm is cut and bent in the form of rectangle whose sides are in the ratio of 5 : 7, what is the length (in cm) of the diagonal of rectangle?

Answer: Option D

Perimeter of rectangle
2(5x + 7x) = 168
5x + 7x = 84
12x = 84
x = 7
Sides of rectangle = 35 cm, 49 cm

$$\begin{array}{rl}& \text{AC}=\sqrt{{35}^2+{49}^2}\\ & \text{AC}=\sqrt{1225+2401}\\ & \text{AC}=\sqrt{3626}\end{array}$$