Rekha opened a recurring deposit account for 20 months. The rate of interest is 9% per annum and Rekha receives ₹441 as interest at the time of maturity. Find the amount Rekha deposited each month.

Given,

n = 20 months

r = 9%

I = ₹441

Let the amount Rekha deposited each month be 'P'.

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

$\therefore 441 = P \times \dfrac{20 \times 21}{24} \times \dfrac{9}{100}\\[1em] 441 = P \times \dfrac{420}{24} \times \dfrac{9}{100}\\[1em] 441 = P \times 17.5 \times 0.09\\[1em] 441 = 1.575P\\[1em] P = \dfrac{441}{1.575}\\[1em] P=₹280$

Hence, Rekha deposited ₹280 each month.