Since there are 60 m of fencing, then the perimeter of the
rectangular fence + the separation fence = 60.
Let x and y
be the sides of the rectangle, let x also be the measure of the fence that separate both
areas.
==> 2x + 2y + x =
60
==> 3x + 2y =
60
==> 3x = 60
-2y
==> x= 20 -(2/3) y
.........(1)
Now we need to determine the maximum area we
could have from using the 60 m fence.
We know that the area
A is:
A = x*y
But from (1) ,
x= 20 -(2/3) y
==> A =
(20-2/3y)*y
==> A =20y -
(2/3)y^2
Now we need to caclulate the maximum value for
A.
First, since the factor of y^2 is negative, then the
function has a maximum value.
Let us find the derivative's
zero.
A1' = 20 - (4/3)y =
0
==> 20 =
(4/3)y
==> y = 20 * 3/4 =
15
==> x= 20 -(2/3)y = 20 - (2/3)*15= 20 - 10 =
10
Then A = 15*10 = 150
m^2
Then the maximum area we could have from
the 60 m fence is 150 m^2 and that by fencing a square area
15X10.
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