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 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)?

What sum of money will amount to Rs. 520 in 5 years and to Rs. 568 in 7 years at simple interest?

A certain sum amounts to Rs 73,255 in 3 years, and Rs 84,525 in 5 years at simple interest. Find the sum.

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.