A certain sum of money becomes Rs 2100 in 4 years and Rs 2550 in 7 years. Find the rate of simple interest per annum.

If a certain sum on compound interest becomes Rs. 2000 in 2 years and Rs. 2200 in 3 years, find rate of interest per annum

If the amounts of a sum of money be Rs. 672 in 2 years and Rs. 714 in years, then find the rate of compound interest per annum.

A certain sum becomes Rs. 6400 in 4 years and Rs. 8200 in 7 years at simple interest. Find the pricipal.

A sum of Rs. 16000 earns a simple interest of Rs. 2560 in 2 years. Find the rate of interest per annum.

A sum of money at compound interest amounts to Rs. 4050 in one year and to Rs. 4723.92 in 3 years. Find the rate of interest per annum.