Question

Shakshi has a recurring deposit account in a bank for 5 years at 9% per annum simple interest. If she gets Rs.51607.50 at the time of maturity, what was her monthly installment?

• A. Rs. 900
• B. Rs. 560
• C. Rs. 700
• D. Rs. 600

Answer 1

The correct option is C

Rs. 700

Let the monthly installment be x,

Total money deposited by Shakshi in 5 years = Rs.60 $\times$ x = Rs.60x.

Principal for 1 month = Rs. x $\times$ (60 + 59 + 58 + … + 3 + 2 + 1)

=Rs. x $\times$ 60 $\frac{(60+1)}{2}$ [Using, Sn = $\frac{n(n+1)}{2}$]

= Rs.1830x.

Interest of Rs.1830x for 1 month at the rate of 9% = Rs.$\frac{(1830x\times 9\times \frac{1}{2})}{100}$

= Rs. $\left(\frac{549}{400}x\right)$

The maturity amount = Rs. 60x + Rs. $\left(\frac{549}{40}x\right)$ = Rs.$\left(\frac{2949}{40}x\right)$.

As per question, $\left(\frac{2949}{40}x\right)$ = 51607.50

Or, x = Rs.$\frac{(51607.50\times 40)}{2949}$ = Rs.700.