Question

Gopal has a cumulative deposit account and deposits Rs. $900$per month for a period of $4$ years. If he gets Rs.$52,020$ at the time of maturity, find the rate of interest.

• A. $5\%$
• B. $2\%$
• C. $10\%$
• D. $12\%$

Answer 1

The correct option is C $10\%$

Installment per month $\left(P\right)=Rs.900$

No. of months $\left(n\right)=4\text{years}=12\times 4=48\text{months}$

Let rate of interest be $r\%$ per annum

$t=\frac{n(n+1)}{2\times 12}=\frac{48\times 49}{24}=98$

$\therefore S.I.=P\times \frac{n(n+1)}{2\times 12}\times \frac{r}{100}$

$\Rightarrow S.I.=900\times \frac{48(48+1)}{2\times 12}\times \frac{r}{100}=Rs.882r$

Maturity value $=Rs.(900\times 48+882r)=Rs(43200+882r)$

maturity value $=Rs.52020$

$\therefore 43200+882r=52020$

$\Rightarrow 882r=52020-43200$

$\Rightarrow r=\frac{8820}{882}=10\%$

Hence, rate of interest $10\%$.