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thin piece of wire

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thin piece of wire

by shibal » Thu Jul 02, 2009 4:13 pm
A thin piece of 40 m wire is cut in two. One piece is a circle with radius of r. Other is a square. No wire is left over. Which represents total area of circle and square in terms of r?

i get [spoiler]pir^2 + (40 - 2pir)^2[/spoiler] but oa is [spoiler]pir^2 + (10 - ½ pir)^2[/spoiler]
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Re: thin piece of wire

by ssmiles08 » Thu Jul 02, 2009 4:46 pm
pi*r^2 + s^2 = Area of circle and square.

2*pi*r + 4*s = 40

pi*r + 2*s = 20

isolate s.

(20 - pi*r)/2 = s

area = pi*r^2 + [(20 - pi*r)/2]^2

simplified to: pi*r^2 + [10 - (pi*r)/2]^2
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