Question

A spherical iron ball of 10 cm radius is coated with a layer of ice of uniform thickness the melts at a rate of 50cm³/min. When the thickness of ice is 5 cm, then the rate (in cm/min.) at which of the thickness of ice decreases, is :

(1) 1/36π

(2) 5/6π

(3) 1/18π

(4) 1/54π

Answer 1

Answer is (3) 1/18π

Answer 2

Answer is (3) 1/18π

Let thickness of ice be 'h'.