Question

At what rate percent will a sum of money double itself in $7years?$

Answer 1

Let the principal be $RsP$.

$$\begin{gathered} A=Rs2P \\ SI=A-P=2P-P=P \\ R=\frac{SI\times 100}{P\times T}=\frac{P\times 100}{P\times 7}=\frac{100}{7}\% \end{gathered}$$