Question

A sum of money triples itself in 15 years 6 months. In how many years would it double itself?

• A. 6 years 3 months
• B. 7 years 9 months
• C. 8 years 3 months
• D. 9 years 6 months

Answer 1

The correct option is B 7 years 9 months

$\Rightarrow$ Let sum be $x$ then, $S.I$ will be $2x$.

$\Rightarrow$ Time = $15\frac{1}{2}years=\frac{31}{2}years$

$\therefore$ $Rate=\left[\frac{100\times 2x}{x\times \frac{31}{2}}\right]\%$

$\therefore$ $Rate=\frac{400}{31}\%$

$\Rightarrow$ Now, $Sum=x,S.I=x$ and $R=\frac{400}{31}\%$

$\Rightarrow$ $Time=\frac{100\times x}{x\times \frac{400}{31}}$

$\Rightarrow$ $T=\frac{31}{4}years$

$\therefore$ $T=7years9months$.