The length of a rectangle is increasing at a rate of 6 cm/s and its width is increasing at a rate of 5 cm/s. when the length is 15 cm and the width is 9 cm, how fast is the area of the rectangle increasing?

By definition, the area of a rectangle is given by:

A = w * l

Where,

w: width

l: long

Deriving this expression we have:

A ' = w' * l + w * l '

Substituting the values:

A ' = (5) * (15) + (9) * (6)

A ' = 129 cm ^ 2 / s

Answer:

The area of the rectangle is increasing at:

A ' = 129 cm ^ 2 / s