Heating a plate. When a circular plate of metal is heated in an oven, its radius increases at the rate of `0.01cm//"min"`. At what rate is the plate's area increasing when the radius is 50 cm ?

Explanation

`A=pi r^(2)`
`rArr " " (dA)/(dt) =2pi r (dr)/(dt)`
` =2 pi xx 50 xx(1)/(100)=pi (cm^(2))/("min")`