Question

A sum of money becomes $\frac{4}{3}$ of itself in 6 years at a certain rate of simple interest. Find the rate of interest.

Answer 1

$$\begin{gathered} \begin{array}{l}\text{Let the sum be Rs}x.\\ \\ \text{Amount =}\frac{4}{3}x\\ \text{S}\text{.I}\text{.=A}-\text{P=}\frac{4}{3}x-x\\ \text{=}\frac{x}{3}\\ \text{Let the rate be R}\%.\\ \\ \text{S}\text{.I.=}\frac{\text{P×R×T}}{\text{100}}\\ =>\frac{x}{3}=\frac{x\times \text{R×6}}{100}\\ =>\text{R}=\frac{\sout{x}\times 100}{\sout{x}\times 6\times 3}=\frac{100}{18}=5.55\end{array} \\ \mathrm{Hence},\mathrm{the}\mathrm{rate}\mathrm{of}\mathrm{interest}\mathrm{is}5.55\%. \end{gathered}$$