Question

If a sum of money at compound interest amounts to thrice itself in 3 years, then in how many years will it be 9 times of itself?

• A. 12 years
• B. 6 years
• C. 9 years
• D. 15 years

Answer 1

Answer: (B)

6 years

According to the question,
Amount = $P{(1+\frac{R}{100})}^n$
$3P=P{(1+\frac{R}{100})}^3\Rightarrow {(1+\frac{R}{100})}^3$
$9P=P{(1+\frac{R}{100})}^n\Rightarrow 9={(1+\frac{R}{100})}^n$
$(3{)}^2={(1+\frac{R}{100})}^n\Rightarrow {\left[{(1+\frac{R}{100})}^3\right]}^2={(1+\frac{R}{100})}^n$
On equating the powers as base is same, we, get n = 6years.