Question

A sum of money placed at compound interest doubles itself in 3 years. In how many years will it amount to 8 times itself?

• A. 9 years
• B. 8 years
• C. 27 years
• D. 7 years

Answer 1

The correct option is A 9 years

Then, $2x=x{[1+\frac{R}{100}]}^3$

$\Rightarrow [1+\frac{R}{100}]=2^{1/3}$ ...(i)

$8x=x{[1+\frac{R}{100}]}^T$

$\Rightarrow 8=[2^{1/3}{]}^T$

$\Rightarrow 2^3=2^{T/3}$

$\Rightarrow \frac{T}{3}=3$

$\therefore T=9yrs.$