Max volume problem, intro calc

[katia11]

Homework Statement

What are the dimensions of the base of the rectangular box of the greatest volume that can be constructed from 100 sq inches of cardboard if the base is to be twice as long as it is wide? Assume the box has no top.

Homework Equations

V box = lwh
A = lw ?

The Attempt at a Solution

I did all the other similar problems assigned but am not sure where to begin here.

Drew a diagram. Base length= 2n width=n
volume=lwh
volume=2n*n*h
volume=2n^2*h

but now what. . .am I all wrong?

Sorry if this is way easy, it's just been awhile since I did these.

 

[Apphysicist]

Since all your material is going into making the box, the area of your material is the surface area of your box. Note that it doesn't have a top.