If a sum doubles in 16 years, how much will it be in 8 years ?

Answer: Option A

Let Sum = Rs. x. Then, S.I. = Rs. x, Time = 16 years
$$\begin{array}{rl}& \therefore \text{Rate}=\left(\frac{100\times x}{x\times 16}\right)\%=\frac{25}{4}\%=6\frac{1}{4}\%\\ & \text{Now, sum}=\text{Rs}\text{. }x,\\ & \text{Time}=8\text{years}\\ & \text{Rate}=6\frac{1}{4}\%\\ & \therefore \text{S}\text{.I}\text{.}=\text{Rs}\text{.}\left(\frac{x\times 25\times 8}{100\times 4}\right)\\ & =\text{Rs}\text{. }\frac{x}{2}\\ & \text{So,}\\ & \text{Amount}=\text{Rs}\text{.}\left(x+\frac{x}{2}\right)\\ & =\text{Rs}\text{. }\frac{3x}{2}\\ & =1\frac{1}{2}\text{ times}\end{array}$$