# Re: Precal functions

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Posted by Brad Paul on September 22, 2002 at 16:17:20:

In Reply to: Precal functions posted by A.C on September 22, 2002 at 15:13:22:

: I dont understand hoe to get the volume of the box in terms of x heres the hole problem.

: An open top box has a surface area of 20sq.units.The base of the box is a square of lenght of x. Express the volume of the box in terms of x.

: thank you for your help:)

What is the area of the bottom of the box in terms of x?

Abottom=x2

We do not know the height of the side of the box. But that is OK we
will just call it h and write our equations as if we knew h's value.

What is the surface area of the four sides of the box?

Ssides=4*x*h

What is the total surface ares of the open top box?

Stotal=Abottom + Ssides = x2+4*x*h

where Stotal=20 sq. units.

Now what is the volume of the box?

V=x2*h

So we need to solve for h and plug it into our volume equation. I
suggest you do the algebra with just the letters then plug in the
numbers.

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