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solong [7]
3 years ago
5

The length and width of a rectangle must add up to 78 feet. calculate the dimensions that will yield the maximum area (remember,

area = length times width). what is the length that results in the maximum area?
Mathematics
1 answer:
denis23 [38]3 years ago
5 0

The length that results in the maximum area is 39 feet.

<u><em>Explanation</em></u>

Lets assume, length of the rectangle is x feet and width of the rectangle is y feet.

As the length and width must add up to 78 feet, so the equation will be...

x+y=78 ................................................(1)

Solving equation (1) for y  : y= 78-x

Now the area of the rectangle,

A = x*y\\\\ A= x(78-x)\\\\ A= 78x-x^2\\\\ A= -x^2 +78x...................(2)

A will be maximum when \frac{dA}{dx} = 0

Now taking derivative of equation(2) with respect to x......

\frac{dA}{dx}= -2x+78

If \frac{dA}{dx} =0, then

-2x+78=0\\\\ -2x=-78\\\\ x=\frac{-78}{-2}=39

If x= 39, then y= 78-x = 78-39=39

So, both length and width will be 39 feet for getting maximum area.

The length that results in the maximum area is 39 feet.


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