"5 WCIC SUITM dlld 15 2TU UN 7.
Two concentric circles are expanding in such a way that the radius of the inner circle is
increasing at the rate of 10 cm/sec and that of the outer circle at the rate of 7 cm/sec. At a
certain time, the radii of the inner and the outer circles are respectively 24 cm and 30 cm.
At what time, is the area between the circles increasing or decreasing? How fast?​