# Minimizing Surface Area

• Jan 31st 2007, 01:31 PM
fdrhs
Minimizing Surface Area
United Parcel Service has contracted you to design a closed box with a square base that has a volume of 5000 cubic inches.

Find a function for the surface area of the box.

NOTE: There is a diagram of a box having length = x, width = x and height = y
• Jan 31st 2007, 01:54 PM
CaptainBlack
Quote:

Originally Posted by fdrhs
United Parcel Service has contracted you to design a closed box with a square base that has a volume of 5000 cubic inches.

Find a function for the surface area of the box.

NOTE: There is a diagram of a box having length = x, width = x and height = y

The area of the base and top are both x^2, the area of each of the four
sides is xy. There for the totl surface area is:

A=2x^2+4xy square inches (assume x and y are in inches).

We are also told that the volume of the box is 5000 cubic inches, but we also
know that the volume of the box is length times breadth times height=x^2y.

so: x^2y=5000, or y=5000/x^2. So now substitute this back into the
equation for the surface area:

A=2x^2+4x(5000/x^2)=2x^2+20000/x square inches.

RonL
• Jan 31st 2007, 03:27 PM
fdrhs
fdrhs
You said:

"...the volume of the box is length times breadth times height."

What does the word BREADTH mean?

I thought the volume is: V = (length) (width) (height)?

• Jan 31st 2007, 05:59 PM
fdrhs
hey
How was I to know this is a calculus question?

The question is found in my pre-calculus textbook.

Why would I post the question in the pre-calculus section?
• Jan 31st 2007, 06:07 PM
Quick
Quote:

Originally Posted by fdrhs
You said:

"...the volume of the box is length times breadth times height."

What does the word BREADTH mean?

I thought the volume is: V = (length) (width) (height)?

• Jan 31st 2007, 08:45 PM
CaptainBlack
Quote:

Originally Posted by fdrhs
How was I to know this is a calculus question?

The question is found in my pre-calculus textbook.

Why would I post the question in the pre-calculus section?

:confused: What are you refering to?

This is definitely a pre-calculus question as asked here, it does not ask you to maximise or find a rate of change of anything, does it? (except in the title)

RonL
• Feb 1st 2007, 02:35 AM
fdrhs
ok
I was given an infraction and threatened here on this site for placing this question in the precalculus section. Is that a crime?

People get kicked out of this site easily, don't they?

I am a newbie and have already been threatened by the tutors here.

Is this wise?

This site will loose its students if this continues.
• Feb 1st 2007, 02:36 AM
Quick
Quote:

Originally Posted by fdrhs
I was given an infraction and threatened here on this site for placing this question in the precalculus section. Is that a crime?

People get kicked out of this site easily, don't they?

I am a newbie and have already been threatened by the tutors here.

Is this wise?

This site will loose its students if this continues.

Obviously this was from ThePerfectHacker.
• Feb 1st 2007, 03:46 AM
CaptainBlack
Quote:

Originally Posted by fdrhs
It does not matter who the e-mail came from.

What did I do to deserve an infraction as a new guy here?

It is a BIG CRIME to post questions in the wrong place BY MISTAKE?????

An infraction is not a big deal here, just lets you know that its not
acceptable to make a habit of whatever its given for.

Also remember that the moderators can become somewhat less tolerant
on days where they have to spend considerable time tidying up rather than
doing something more interesting.

I forget the exact numbers, but you need multiple infractions within a few
days of one another to qualify for a short ban.

RonL