If the rate of change of area of a circle is equal to the rate of cha…

area = $πr^2$ diameter = $2r$

so $\frac{d(πr^2)}{dt}=\frac{d(2r)}{dt}$

$2πr\frac{dr}{dt}=2\frac{dr}{dt}$

$⇒r=\frac{1}{π}$ unit