Question

A sum of money invested at a certain rate of simple interest double itself in 12years 6months. It will be trible itself at the same rate of interest in

Answer 1

Let sum invested be, P x.

time , t = 12.5 yrs

Amount, A = 2x as got doubled

So, interest = A - P = 2x - x = x

let r be the rate %

Also, interest = Prt/100

so, x = xr12.5/100

or, r = 100/12.5 = 8 %

Now new A = 3x

r = 8%

let time be t to get the sum triple

so, interest = 3x - x = 2x

Also, 2x = x8t/100

so, t = 100/4 = 25 yrs

Hence in 25 yrs the sum will get triple.