What sum of money will amount to Rs. 520 in 5 years and to Rs. 568 in 7 years at simple interest?

Answer: Option A

(Principal + Interest) in 5 years → 520
(Principal + Interest) in 7 years → 568
$$\begin{array}{rl}& \therefore \text{Interest in 2 years = 48}\\ & \therefore \text{I = }\frac{\text{48}}{2}\\ & \text{ = Rs}\text{. 24 in one year}\\ & \therefore \text{P = 520 - 24}\times \text{5}\\ & \text{ = Rs}\text{. 400}\end{array}$$