A principal amounta double in `20` years at a certain rate of simple interest. At the same rate of interest the principal amounts triple in-

Options

A. `30` years
B. `33` years
C. `40` years
D. `45` years

Explanation

Let the principal be Rs `x` and the rate of simple interest be `r%`
As per question, the amount `=Rs2x` in `20` years
`:.` Interest `=Rs(2x-x)=Rsx`
`:.(x xx r xx20)/(100)=x`[by formula]
`impliesr=(100xx x)/(x xx20)=5`
`:.` The required yearly rate of simple interest `=5%`
If this principal amounts `Rs3x`. then the interest `=Rs(3x-x)=Rs2x`
`:.(x xx5xxt)/(100)=2ximpliest=(2x xx100)/(x xx5)=40`.
`:.` The required time `=40` years