The yearly income of Amalbabu becomes `Rs60` less when yearly rate of simple interest becomes `3(3)/(4)%` decreasing from `4%`. Then find the principal of Amalbabu.

Explanation

Let the principal of Amalbabu be `Rsx`
Then the interest of `1` year at the rate of `4%=Rs(x xx4xx1)/(100)=Rs(x)/(25)`
Also, at the rate of `3(3)/(4)%=(15)/(4)%`
the interest of `1` year `=Rs(x xx15xx1)/(4xx100)=Rs(3x)/(80)`
As per question, `(x)/(25)-(3x)/(80)=60`
`implies(16x-15x)/(400)=60`
`implies(x)/(400)=60impliesx=400xx60=24000`
`:.` The principal of Amalbabu `=Rs24000`.