Discussion Forum

The sum of money at compound interest doubles itself in 5 years. It will amount to eight times itself at the same rate of interest in

Answer:

Explanation:

Suppose sum $=P$ ;Rate $=R\%$ ; $T=5$ yrs ; $A=2P$

$2P$ $=\left[P\left(1+\frac{R}{100}\right)^{5}\right]$

$1+\frac{R}{100}$ $=2\times\frac{1}{5}$

Now let amount becomes $8$ times in $x$ years

$8P$ $=\left[P\left(1+\frac{R}{100}\right)^{N}\right]$

$\Rightarrow 8$ $=\left(1+\frac{R}{100}\right)^{N}$

$\Rightarrow N$ = 15 Yrs