Question

In what time will Rs. 4000 amount to Rs. 5324 at 10% per annum compound interest?

• A. $1$ years
• B. $2$ years
• C. $3$ years
• D. $4$ years

Answer 1

The correct option is C $3$ years

Given that, $P=Rs.4000,A=Rs.5324$ and $R=10\%$

Let the time be $T$ years

We know that, for compound interest,

$A=P\times {(1+\frac{R}{100})}^T$

$\therefore 5324=4000\times {(1+\frac{10}{100})}^T$

$\Rightarrow$ $\frac{5324}{4000}={(1+\frac{1}{10})}^T$

$\Rightarrow$ $\frac{1331}{1000}={\left(\frac{11}{10}\right)}^T$

$\Rightarrow$ ${\left(\frac{11}{10}\right)}^3={\left(\frac{11}{10}\right)}^T$

$\therefore$ $T=3years$.

Hence, $Rs.4000$ will amount to $Rs.5324$ at $10\%$ per annum in $3$ years.