A sum invested at compound interest amounts to Rs. 7,800 in 3 years and Rs. 11,232 in 5 years. What is the rate per cent?

Question

Question

This question was previously asked in

SSC CGL 2021 Tier-I (Held On : 11 April 2022 Shift 2)

Answer 1

Given:

The Sum becomes Rs. 7800 in 3 years and Rs. 11232 in 5 years

Formula used:

At compound interest, the final amount = \(P\left(1+\frac{r}{100} \right)^{n}\)

Where, P = The sum of the amount

r = Rate of interest

n = Time (years)

Calculation:

Here, Rs. 7800 becomes Rs. 11232 at compound interest in two years.

Let, the rate of interest = R

So, 11232 = \(7800\left(1+\frac{R}{100} \right)^2\)

⇒ [(100 + R)/100]² = 11232/7800

⇒ [(100 + R)/100]2 = 144/100

⇒ [(100 + R)/100]2 = (12/10)²

⇒ [(100 + R)/100] = (12/10)

⇒ 100 + R = 1200/10 = 120

⇒ R = 120 - 100 = 20

∴ The rate per cent is 20%

Download Solution PDF