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Help, math homework X_X

Name: Anonymous 2008-07-04 16:27

Dear 4chan math gurus,
I'm stuck on this math problem in my precalc book.  I'm hoping someone here could tell me how to solve it.  I already know the answer, I just need to know it's solved.  Here it is:

"A rectangular playground is to be fenced off and divided in two by another fence parallel to one side of the playground.  Six hundred feet of fencing is used.  Find the dimensions of the playground that maximize the total enclosed area.  What is the maximum area?"

Answer: 150 by 100 ft.  Total of 15000 ft^2

The last time I had a problem like this, I followed a model like this:

Perimeter = 3x + 2y
Area = xy

P = 600 = 3x + 2y
2y = 600 - 3x
y = (600 - 3x)/2
A = xy
A = x[(600 - 3x)/2]

This is where I get stuck.  If anyone had a better method or could (preferably) show me how I can get the answer through something along the lines of the above method, then I'd really appreciate it.  Thanks in advance.

Name: Anonymous 2008-07-12 8:23

>>7
Excuse me bro, but >>5 didn't use differentiation, he showed you how to find the max and min without using differentiation, thus demonstrating that the max area will be obtained with x = 100.

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