A sum of money becomes triple in 10 years at simple interest. Find the rate of interest.
Correct: C
Let the principal amount be P and the rate of interest be R. We are given that the amount becomes triple in 10 years, which means the amount after 10 years is 3P. The simple interest is given by the formula I = PRT/100, where I is the interest. Since the amount after 10 years is 3P, the interest is 2P. Substituting these values in the formula, we get 2P = P * R * 10 / 100, which implies R = 20.