# Optimisation using calculus

1. Mar 17, 2013

### Elihu5991

1. The problem statement, all variables and given/known data
SEE QUESTION IMAGE

2. Relevant equations
SEE ABOVE

3. The attempt at a solution
SEE WORKINGS IMAGE

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• ###### Scan.jpeg
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2. Mar 17, 2013

### ehild

Can you type in your work?

ehild

3. Mar 17, 2013

### Elihu5991

Sorry that my handwritiing is too messy and scan isn't done right. Just trying to get this done ASAP.

(25-2x)(40-2x)

y=(25-2x)(-2)+(40-2x)(-2)
=-50+4x-40+2x
=-90+6x
x=15

Not sure what to next do.

4. Mar 17, 2013

### Ray Vickson

Is x the length of the corner pieces cut out? If so, you need to define it in words; a formulation without an explanation is worth 0.

Also, is (25-2x)*(40-2x) the thing you want to maximize? Why? What does the box look like if you use your proposed solution of x = 15?

5. Mar 17, 2013

### eumyang

You mean y', not y.

Also, I'm guessing that you want to maximize the volume. If so, then
y = (25-2x)(40-2x)
as the volume equation would be wrong. You're missing the height. What would it be?