Question

What sum will become $Rs9261$ after $3$ years at $5\%$ per annum compound interest?

Answer 1

If an amount P is invested for $n$ years at $r\%$ per annum we will get an amount ${}^{\prime }{A}^{\prime }$

$\Rightarrow A=P{(1+\frac{r}{100})}^n$

$\Rightarrow A=9261$ $r=5\%p.a.$ $n=3years$

$\therefore 9261=P{(1+\frac{5}{100})}^3$

$\Rightarrow 9261=P{(1+\frac{1}{20})}^3$

$\Rightarrow 9261=P{\left(\frac{21}{20}\right)}^3$

$\Rightarrow 21\times 21\times 21=P\frac{\left(21\right)\times \left(21\right)\times \left(21\right)}{8000}$

$\Rightarrow P=Rs.8000$

Hence, the answer is $Rs.8000.$