The length x of a rectangle is decreasing at the rate of 2 cm/minute and the width y is decreasing at the rate of 3 cm/minute. When x =10cm and y = 10 cm, find the rates of change of the perimeter of the rectangle.

10 cm/m 20 cm/m -20 cm/m -10 cm/m

-10 cm/m

dP/dt = 2( dx/dt + dy/dt)