At what rate of simple interest in percent per annum , a some of money becomes double in `15` years?

If at the rate of simple interest in percent per annum by which a principal becomes double in 20 years and also amounts to 7Rs20 after 4 years, then find the principal.

Find the rate of simple interest per annum, if a sum borrowed becomes double in 5 years.

At the same rate of simple interest in percent per annum, if a principal becomes the amount of Rs 1248 in 7 years and or Rs 1056 in 4 years. Find the principal and rate of simple interest in percent per annum.

At what rate of simple interest in percent per annum, the ratio of principal and its interest after 20 years is 1:1 ?

At the same rate of simple interest in percent per annum, if a principal becomes are amount of Rs 7100 in 7 yrs and of Rs 6200 in 4 yrs, then find the principal and rate of simple interest in percent per annum.

At the same rate of simple interest in percent per annum, if a principal becomes the amount of 7100Rs in 7 years and of 6200Rs in 4 years. Determine the principal and rate of simple interest in percent per annum.

Find the rate of simple interest in percent per annum if the simple interest of a principal is 3/5 part of the amount in 10 years.

A certain principal amounts Rs2750 in 2 years at a rate of simple interest of 5% per annum. Then find the rate of simple interest in percent per annum for which the principal amounts Rs3000 in 2 years.