A sum becomes 6 times of itself in 4 years at compound interest (interest is compounded annually). In how many years will the sum becomes 216 times of itself?
Show answer & explanation
Correct answer: A
Explanation
The correct answer is option 1 i.e. 12
Let the principal be P
⇒ P(1 + R/100)4 = 6P
⇒ (1 + R/100)4 = 6
⇒ (1 + R/100) = 61/4 ...... (1)
Let the amount after T years be 216P
⇒ P(1 + R/100)T = 216P
Substituting the (1) in the above equation
⇒ (61/4)T = 216
⇒ 6T/4= 61/3
⇒ T/4 = 1/3
⇒ T = 12 years