A sum of money (P) doubles in 10 years. In how many years it will be triples at the same rate of simple interest?

The problem is based on the formula for simple interest, which is I = PRT, where I is the interest, P is the principal amount, R is the rate of interest, and T is the time.

Given that the sum of money doubles in 10 years, this means that the interest earned in 10 years is equal to the principal amount. So, we can write the equation as P = P * R * 10. Simplifying this, we get R = 1/10 or 10%.

Now, we want to find out when the sum of money will triple. This means that the interest earned will be twice the principal amount. So, we can write the equation as 2P = P * R * T. Substituting the value of R from above, we get 2P = P * 10% * T. Simplifying this, we get T = 20 years.

So, the sum of money will triple in 20 years at the same rate of simple interest.