Question

Shahrukh opened a Recurring Deposit Account in a bank and deposited Rs. $800$ per month for $1\frac{1}{2}$ years. If he received Rs. $15,084$ at the time of maturity, find the rate of interest per annum.

Answer 1

Here, $P=$ money deposited per month $=$ Rs. $800$

$n=$ Time for which the money is deposited $=1\frac{1}{2}$ years $=18$ months.

Let the rate of interest be $r\%$ per annum, then

Interest $=P\times \frac{n(n+1)}{2\times 12}\times \frac{r}{100}$

$=800\times \frac{18\times 19}{2\times 12}\times \frac{r}{100}$

$=$ Rs. $114r$

Total money deposited $=18\times 800=$ Rs. $14,400$

Since money deposited $+$ interest $=$ Maturity value

$\Rightarrow 14,400+114r=15,084$

$\Rightarrow 114r=15,084-14,400$

$\Rightarrow 114r=684$

$\Rightarrow r=\frac{684}{114}=6$

Hence, rate of interest $=6\%$ p.a.