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 May 1, 2016
 #1
avatar+37170 
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Let x= the perpindicular sides   total fence needed = 5x

the remaining LONG side of the fence (opposite the building) will then be 210 - 5x

the area will then be  x (210-5x) = 210x -5x^2 = area 

Take derivative and set to zero to find 'x' that makes biggest area:

 

210 -10x = 0   10x= 210  x= 21       5x = 105     Long side = 105

Total area will be    21 x 105 = 2205 sq ft    and each area will be 551.25 sq ft

 

 

Sorry!  Made a math error there!  

 May 1, 2016
edited by Guest  May 1, 2016
 #2
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It is wrong though

 May 1, 2016
 #3
avatar+130516 
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Let x be the longer side of the rectangle and let y be the shorter side of the rectangle

 

And the expression for the total fencing used is

 

210  = x + 5y    solving for y, we have

 

y = [ 210 - x] / 5      this will be one side of a kennel

 

The other side will  =  the long side divided by 4 =  x  / 4

 

So....the area of one kennel =

 

[x /4] * [210 -x]/ 5   simplify

 

[210x - x^2] / 20  =

 

(-1/20)x^2  + 10.5x

 

We can find the x that maximizes this by    -b/2a     where b = 10.5 and a = -1/20

 

So we have

 

-10.5 / [ 2 (-1/20)]   =    10.5 / (1/10)   =  105 ft   ....and this is the length of the longest side

 

So  the length of the top side of one kennel = 1/4 of this = 105/4 ft  = 26.25 ft

 

And the length of the other side of one kennel  = [210 - 105] / 5   = 105/5 = 21 ft

 

So.....the dimensions that maximize the area of each kennel =  26.25 ft x 21 ft

 

 

cool cool cool

 May 1, 2016
 #4
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Thank You so much for the help, CPhill!!!cool

 May 1, 2016

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