Answer:
76cm/s
Step-by-step explanation:
Let the length = L
width = W
A = LW
[tex]\frac{dL}{dt} = 7 cm/s[/tex] (the rate at which the length is changing)
[tex]\frac{dW}{dt} = 3cm/s[/tex] ( the rate at which the width is changing)
[tex]\frac{dA}{dt} = L(\frac{dW}{dt} + W(\frac{dL}{dt} )[/tex] Product Rule
[tex]\frac{dA}{dt} = 9(3) + 7(7)[/tex]
[tex]\frac{dA}{dt} = 27 + 49[/tex]
[tex]\frac{dA}{dt} = 76 cm/s[/tex]
