A sum of money becomes 4 times itself in 10 years at simple interest. What is the rate of interest per annum?
Q1. A sum of money becomes 4 times itself in 10 years at simple interest. What is the rate of interest per annum?
Answer: 30%
Explanation: Simple interest formula: A = P(1 + rt), where A = 4P, t = 10. So, 4P = P + P*r*10, simplifying to 3 = 10r, hence r = 30%.