A sum of money doubles itself in 10 years on compound interest. In how many years will it become four times?
Answer & explanation
Correct answer: option 2
The correct answer is Option (2) → 20
At compound interest the amount is multiplied by the same factor in every equal period. If the sum doubles in 10 years, it doubles again in the next 10 years.
In the first 10 years: \(P\rightarrow2P\)
In the next 10 years: \(2P\rightarrow4P\)
Time to become four times \(=10+10=\) 20 years