Question

sam deposited Rs. 350 per month for 6 years in a recurring deposit account in a post office. If she received Rs.32,865, then what is the rate of interest?

Answer 1

You can use Recurring Deposit Maturity Value Formula to solve this:
\[M = \frac{ R [(1+r)^{n} - 1 ] }{ (1-(1+r)^{-1/3}) }\]
Where,
M = Maturity value
R = Monthly Installment
r = Rate of Interest (i) / 400
n = Number of Quarters
At the end of every month, you put Rupees 350 in to recurring deposit that pay r%, compounded monthly.
So, the Future Value after 6 years (72Months) is Rs.32,865
Then, M = 32,865; i=r%/12; N = 72; R = 350
By substituting these values in RD Formula u can find the rate of interest.