If the radius of a circle is decreased by 50% , find the percentage decrease in its area.

let original radius = r and  new radius = (50/100) r = r/2

original area =  $\mathrm{\pi r}2$ and new area =  $\pi r/22$

decrease in area =  $3\mathrm{\pi r}2/4$* $\frac{1}{\mathrm{\pi r}}$ *100 = 75%