Correct Answer - Option 3 : 45 years
Formula used:
Amount = Principal × (1 + r/100)n
Calculation:
Given that a sum of money doubles itself at compound interest in 15 years.
⇒ 2P = P(1 + r/100)15
⇒ 2 = (1 + r/100)15 ----(i)
For Sum to become 8 times
⇒ 8P = P(1 + r/100)n
⇒ 8 = (1 + r/100)n
⇒ (2)3 = (1 + r/100)n
⇒ {[1 + r/100]15}3 = (1 + r/100)n {From (i)}
⇒ (1 + r/100)45 = (1 + r/100)n
⇒ n = 45
∴ Time taken = 45 years
