Question

A certain sum of money doubles in 8 years .In how much time it becomes 4 times of itself at the same rate of simple interest?
Plz give description

Answer 1

let the simple interest be I
according to the formula of simple interest I = $\frac{PRI}{100}$
now after 8 years the principal becomes 2P therefor simple interest will be 2P-P=P so P=P*R*8/100
therefore rate of interest is 100/8
now we need simple interest = 3P because then final principal will be 4P 
so 3P = P*100*T/800 = T = 24 years