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Circle perimeters (Posted on 2002-11-19) Difficulty: 2 of 5
Prove that the sum of the perimeters of the smaller circles in the Bigger circle is equal to that of the bigger circle. (The centres are on the line given which is the diameter of the bigger circle.)

See The Solution Submitted by Dulanjana    
Rating: 2.3846 (13 votes)

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Solution solution | Comment 3 of 9 |
perimeter = 2*pi*radius
radius = diameter/2

disignate diameter of the large circle to D
designate teh diameters of the small circles from left to right as d1, d2, d3 and d4

The drawing shows D=d1+d2+d3+d2
Therefore D/2= (d1+d2+d3+d4)/2 OR (d1/2) + (d2/2) + (d3/2) + (d4/2)
radius = dimaeter /2
therefore R (radius large circle = r1+r2+r3+r4 (other radii)

THerefore

P (perimeter large) = 2 * pi * R
p1 = 2 * pi * r1
p2 = 2 *pi * r2
p3 = 2 * pi * r3
p4 = 2 * pi * r4

p1+p2+p3+p4 =
(2*pi*r1)+(2*pi*r2)+(2*pi*r3)+(2*pi*r4)=
2 * pi *(r1 + r2 + r3 + r4) =
2 * pi * R =
P =

QED

  Posted by Andrwe Mitchell on 2003-07-25 08:24:36
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