At what rate of simple interest a certain sum will be doubled in 15  years?

At what rate of simple interest a certain sum will be doubled in 12 years ?

At what rate of simple interest a certain sum will be doubled in 14 years

Find the rate of Simple interest by which a given money is doubled in 15 years

2400 becomes 2976 in 3 years at a certain rate of simple interest. What sum of money will become 5016 in 4 years at the same rate of interest?

at what rate per annum simple interest will a sum double it self in 2 years?