Question

Renu has a cumulative deposit account of
200 per month at 10% per annum. If she gets
6775 at the time of maturity, find the total time
for which the account was held.​

Answer 1

hope this answer will be helpful

Answer 2

Renu deposited 200 Rs. for 30 months.

Step-by-step explanation:

Let the account was held for n months.

The amount of monthly deposit 'P' = 200

Rate of interest =  10%

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

             =  $200\times \frac{n(n+1)}{2\times 12}\times \frac{10}{100}$

             $=\frac{5n(n+1)}{6}$

Maturity value = deposited amount + interest

$6775=200n+\frac{5n(n+1)}{6}$

$6775=\frac{5}{6}n^2+\frac{1205}{6}n$

$\frac{-5}{6}n^2+\frac{-1205}{6}n +6775=0$

Use quadratic formula for a = -0.834 b = -200.834 c = 6775

$n=\frac{-(-200.834)\pm\sqrt{(-200.834)^2-4(-0.834)(6775)} }{2(-0.834)}$

n = -271, 30

cumulative months can not be in negative form,

therefore, n = 30

Renu deposited 200 Rs. for 30 months.

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