A sum amounts to Rs. 5600 in 4 years and Rs. 6400 in 6 years at a certain rate of simple interest. Find the rate of interest per annum and the sum.

A certain sum of money amounts to Rs 4200 in 3 years and to Rs 6000 in 6 years at simple interest. Find the rate of interest.

A sum of money amounts to Rs 10000 after 5 years and Rs 15000 after 8 years at the same rate of simple interest. Find the rate of interest per annum

A sum of money amounts Rs. 800 in 3 years and Rs. 840 in 4 years at compound interest. What is 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 certain sum of money amounts to Rs. 918 in 2 years and Rs. 969 in 3.5 years at simple interest. What is the rate of interest (in % per annum)?