SOLUTION: Four circles, each of radius 5 inches, fit tightly in a square 20 inches on a side. Each circle is tangent to two other circles. What is the area, to the nearest tenth of a squar

Algebra ->  Circles -> SOLUTION: Four circles, each of radius 5 inches, fit tightly in a square 20 inches on a side. Each circle is tangent to two other circles. What is the area, to the nearest tenth of a squar      Log On


   



Question 77121: Four circles, each of radius 5 inches, fit tightly in a square 20 inches on a side. Each circle is tangent to two other circles. What is the area, to the nearest tenth of a square inch, of the region enclosed by the four circles, at the center of the square
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
What I decided to do is divide the square into 4 equal squares.
Then I look at just 1 circle inside its own square, tangent to
the sides with 4 areas left over in the corners.
The area of the circle is pi%2Ar%5E2+=+25%2Api
The area of the square is 10%2A10+=+100
The area of 1 of the 4 corner areas is %28100+-+25%2Api%29+%2F+4
In the center, ther are 4 of these little corner areas,
so the center area is 4%2A%28100+-+25%2Api%29+%2F+4+=+100+-+25%2Api
100+-+25%2Api+=+21.5 in2 answer
To check the answers, there are 16 of the %28100+-+25%2Api%29+%2F+4
areas in all, so 4 circles + 4%2A%28100+-+25%2Api%29 should equal
20%2A20+=+400
4%2A25%2Api+%2B+4%2A%28100+-+25%2Api%29+=+400
314.16+%2B+4%2A21.46+=+400
314.16+%2B+85.84+=+400
400+=+400
OK