2020 · Q116
A sum triples in ten years under compound interest at a certain rate of interest, the interest is being compounded annually. In how many years, it would become nine times?
general-mental-abilityquantitative-aptitude
- A20 years
- B30 years
- C40 years
- D50 years
Explanation
Tripling in ten years means (1+r)¹⁰ = 3. Nine times is 3² = (1+r)²⁰, so the sum becomes nine times in 20 years.