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40m wire

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40m wire

by okigbo » Fri Oct 30, 2009 3:35 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?
a. Πr2
b. Πr2 + 10
c. Πr2 + ¼ π2r2
d. Πr2 + (40 - 2πr)2
e. Πr2 + (10 - ½ Πr)2
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by truplayer256 » Fri Oct 30, 2009 3:56 pm
Circumference of a circle= 2*pi*r

Perimeter of a square=4*s. S represents the length of each side of the square.

2*pi*r+ 4s= 40

Total area of the circle and square= pi*r^2+s^2

Express s in terms of r.

40-2*pi*r/4=10-(pi*r)/(2)

Total area of the circle and square in terms of r:

pi*r^2+(10-(pi*r)/(2))^(2)

E should be your answer.
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