SOLUTION: COMPARING AREAS a wire 360in long is cut into two pieces. one piece is formed into a square and the other is formed into a circle. if the two figures have the same area, what are

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Question 829937: COMPARING AREAS
a wire 360in long is cut into two pieces. one piece is formed into a square and the other is formed into a circle. if the two figures have the same area, what are the lengths of the two pieces of wire(to the nearest tenth of an inch)

Answer by Edwin McCravy(20056) About Me  (Show Source):
You can put this solution on YOUR website!

The area of the square is s%5E2
The area of the circle is pi%2Ar%5E2

The perimeter of the square is 4s
The circumference of the circle is 2pi%2Ar

%28matrix%284%2C1%2CArea%2C+of%2C+the%2C+square%29%29%22%22=%22%22%28matrix%284%2C1%2CArea%2C+of%2C+the%2C+circle%29%29

So  s%5E2%22%22=%22%22pi%2Ar%5E2

%28matrix%284%2C1%2CPerimeter%2C+of%2C+the%2C+square%29%29%22%22%2B%22%22%28matrix%284%2C1%2CCircumference%2C+of%2C+the%2C+circle%29%29%22%22=%22%22%28matrix%284%2C1%2CLength%2C+of%2C+the%2C+wire%29%29

So  4s%22%22%2B%22%222pi%2Ar%22%22=%22%22360

That equation can be divided through by 2, so we have

    2s%22%22%2B%22%22pi%2Ar%22%22=%22%22180

So we have this system of two equations in two unknowns:

system%28s%5E2=pi%2Ar%5E2%2C4s%2Bpi%2Ar=180%29

Solve the bottom equation for one of the letters and substitute
it in the first equation, getting a quadratic.
You'll get two solutions for (s,r):

First solution:
s+=+180%2F%282%2Bsqrt%28pi%29%29=47.71430138,   r=180%2F%282sqrt%28pi%29%2Bpi%29=26.91991183   

Second solution
 s+=+-180%2F%28sqrt%28pi%29-2%29=791.0483246,   r+=+180%2F%28pi-2sqrt%28pi%29%29=-446.3012248  

We ignore the second solution 

The perimeter of the square is 4s+=+4%2A47.71430138=190.8572055%29
The circumference of the circle is 2pi%2Ar+=+2pi%2A26.91991183+=+169.1427945

As a check add those together and you get 360.

Answers rounded to the nearest tenth of an inch: 

Length of piece formed into a square = 190.9 inches
Length of piece formed into a circle = 169.1 inches 

Edwin