What will be the dimensions of Joe’s dog pen?

Question

Joe will build a rectangular pen for his dog. A wall will form one side of the pen. Joe has 40 ft of fencing to form the other three sides.

Joe plans to build the pen so that it has its maximum possible area.
 

What will be the dimensions of Joe’s dog pen?

Enter your answers in the boxes.

______ ft by____  ft

Answer 1

w represents the width

40 - 2w represents the length

 

f(w) = w(40 - 2w)

Determine the zeros

0 = -2w² + 40w

0 = 2w² - 40w

 

Maximum at 40/(4 or a width of 10 feet