Question

The difference between the $C.I.$ and $S.I.$ on $Rs.8400$ for $2$ years is $Rs.21$ at the same rate of interest per year. Find the rate of interest.

Answer 1

$D=P{\left(\frac{r}{100}\right)}^2$

$21=8400{\left(\frac{r}{100}\right)}^2$

$1=4\frac{r^2}{100}$

$r^2=25$

$r=5$%