A rectangle has a length of 11 inches and a width of 10 inches whose sides are changing. The length is decreasing by 5 in/sec and the width is shrinking at 4in/sec.

Question

What is the rate of change of the area?

Answer 1

Area = Length * Width

A = L * W

dA/dt = L * dW/dt + dL/dt * W

= 11 * (-4) + (-5) * 10

= -44 + -50

= -94