At the same rate of simple interest in percent per annum, if a principal becomes the amount of `7100Rs` in `7` years and of `6200Rs` in `4` years. Determine the principal and rate of simple interest in percent per annum.

Explanation

`:.` Interest of `4` years `=Rs(900x4)/(3)=Rs1200`
`:.` Principal `=Rs(6200-1200)=Rs5000`
Let the rate of simple interest in percent per annum be `r%`
`:.(5000xxrxx4)/(100)=1200impliesr=(1200xx100)/(5000xx4)=6`
`:.` Principal `=Rs5000` and rate of interest in percent per annum `=6%`