Question

Sheela has a cumulative deposit account in Bank and deposits Rs. 300 the bank is 10% p.a. If the maturity value of her deposits is Rs. 7950, find the total time for which the account is held.'

Answer 1

Given that
Sheela Deposits Rs. 300
Rate of Interest = 10% p.a
Maturity value of her deposits = 7950
Let 'n' be the number f months for which the account was held. Maturity value $=300\times n+\frac{300\times n\times (n+1)}{2}\times \frac{10}{100}\times \frac{1}{12}\Rightarrow 7950=300n+\frac{5}{4}(n^2+n)$
(on dividing the above equation by 5 we get)
$\Rightarrow 1590=60n+\frac{1}{4}(n^2+n)\Rightarrow n^2+241n-6360=0\Rightarrow (n+265)(n-24)=0\Rightarrow n=24,-265\Rightarrow n=24$
($\because$ Number of months cannot be -ve)
So, that account was held for 24 months or 2 years.