SOLUTION: A cylindrical wire frame for a wastebasket has a wire circle for the top and bottom, and SIX straight wire rods that hold the top and bottom circles together. The total amount of w
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Question 822130:  A cylindrical wire frame for a wastebasket has a wire circle for the top and bottom, and SIX straight wire rods that hold the top and bottom circles together. The total amount of wire used is 6m. What radius and height will maximize the volume of the cylindrical frame?
This is an optimization problem. I'm stuck /:
So far I have v=pir^2h
2pi r + 2pi r + 6h=6
Which expresses the surface area.
I tried to solve for h and got that h= 6-4pi r over 6
At this point I really don't know what to do next . Any help is greatly appreciated.
This is a grade 12 optimization problem  
Answer by htmentor(1343)   (Show Source): You can put this solution on YOUR website!
 You are definitely on the right track.  This is an optimization problem, and we are trying to maximize the enclosed volume.  
, and the volume will be maximized where dV/dr = 0.  You have already expressed h as a function of r using the information provided.
So we make the substitution before taking the derivative:
Taking the derivative and setting equal to zero you will end up with an expression like 
Since r=0 is not a solution, we are left with  or 
Now solve for h:
The graph of the volume as a function of r is shown below.  We can see the volume maximizes at r = , a little over 0.3.
 
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