If the compound interest on a certain sum for two years at 10% p.a. is Rs. 2,100, then the simple interest on it at the same rate for two years will be

To solve this problem, we need to understand the difference between compound interest and simple interest.

Compound interest is calculated on the initial principal and also on the accumulated interest of previous periods of a deposit or loan. In this case, the compound interest for two years is Rs. 2,100 at a rate of 10% per annum.

Simple interest is calculated only on the original principal.

Given that the compound interest for the second year is the simple interest for the first year plus 10% of the simple interest for the first year (since compound interest includes interest on interest), we can set up the following equation:

Compound Interest = 2 * Simple Interest + 0.10 * Simple Interest

Substituting the given compound interest:

2,100 = 2 * Simple Interest + 0.10 * Simple Interest

Solving this equation for Simple Interest gives:

Simple Interest = 2,100 / 2.1 = Rs. 1,000

So, the simple interest on the sum at the same rate for two years would be Rs. 1,000.