Question

How to find the correct unit of measurement? I am struggling with this. What is the difference between ft³, ft and ft²? Example: 
the length of a rectangular play area is 40 ft. The width of the play area is 20 ft. 

Which is the correct unit of measurement to use when figuring out how much fence is needed to surround the play area?

A.
ft³

B.
ft

C.
ft²

Answer 1

Feet cubed is used when finding volume, feet squared is used when finding area, and feet is used when finding length, so in this case you would use feet

Answer 2

if you want to determine the perimeter / length, use a normal measure - ft.
The area is $ft^{2}$
and the volume $ft^{3}$