A sum of ₹7,000 deposited at compound interest becomes triple of itself after 4 years. How much will the amount be after 12 years?
Answer & explanation
Correct answer: option 3
Three times of sum = 3 × 7000 = 21000
Amount = P$(1 \;+\; \frac{R}{100})^t$
21000 = 7000 [ 1 + \(\frac{R}{100}\) ]4
3 = [ 1 + \(\frac{R}{100}\) ]4
To find sum after 12 years.
On cubing both side,
3³ = [ 1 + \(\frac{R}{100}\) ]¹²
27 = [ 1 + \(\frac{R}{100}\) ]¹²
So, Sum becomes 27 times of itself after 12 years .
i.e. 27 × 7000 = Rs. 189000