The compound interest on a certain sum of money for $2$ years is $Rs 1331.20$ and the simple interest on the same sum for the same time period and at the same rate is $Rs 1280.$ Find the sum and the rate of interest per annum.

On what sum will the difference between the simple and compound interest for $3$ years at $10\%$ p.a. is $Rs 232.50$?

The simple interest on a certain sum for $3$ years is $Rs 1080$ and the compound interest on the same sum at the sum rate for $2$ years is $Rs 741.60$. Find the rate of interest.

The simple interest on a certain sum for $3$ years is $Rs 1080$ and the compound interest on the same sum at the sum rate for $2$ years is $Rs 741.60$. Find the principal.

Sudarshan invested $Rs 60000$ in a finance company and received $Rs 79860$ after $1\frac{1}{2}$ years. Find the rate of interest per annum compounded half-yearly.