Rs.16 becomes Rs.81 in four years at compound interest. The rate of interest per annum is:
Answer & explanation
Correct answer: option 2
In 3 years : Principal : Amount = 16 : 81 = (2)4 : (3)4
In 1 year : Principal : Amount = \(\sqrt[4]{2^4 }\) : \(\sqrt[4]{3^4 }\) = 2 : 3
Interest = 3 - 2 = 1R
Interest rate = \(\frac{1}{2}\) × 100% = 50%