Question: If a sum of money doubles itself in 5 years at simple interest, what will be the rate of interest per annum?
Options:
Correct Answer: 10%
Solution:
Using the formula for simple interest, SI = PRT, where SI = Principal, R = Rate, and T = Time. If the principal doubles in 5 years, then SI = P. Therefore, P = PRT implies R = 1/5 = 20%. Hence, the rate of interest is 10%.