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The figure above shows a cord around two circular disks. If

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The figure above shows a cord around two circular disks. If [#permalink]  01 Dec 2007, 10:38
The figure above shows a cord around two circular disks. If the radii of the two disks are 80 centimeters and 60 centimeters, respectively, what is the total length, in centimeters, of the cord?

(A) 210π

(B) 210π + 280
(C) 280π

(D) 280π + 80
(E) 280π + 280
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Re: geometry - difficult [#permalink]  09 Jun 2008, 06:57

160pi*3/4 +120pi*3/4 + 2*80+2*60= 210pi+280
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Re: geometry - difficult [#permalink]  10 Jun 2008, 03:18
marcodonzelli wrote:
The figure above shows a cord around two circular disks. If the radii of the two disks are 80 centimeters and 60 centimeters, respectively, what is the total length, in centimeters, of the cord?

(A) 210π

(B) 210π + 280
(C) 280π

(D) 280π + 80
(E) 280π + 280

another B
basically 3/4 of the circumference of each circle + 2*radius of each circle

= 120pi + 90pi + 160 + 120
= 210pi + 280
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Re: geometry - difficult [#permalink]  10 Jun 2008, 06:37

haha...

just kidding..but if you could draw it again more acurately then it would be great!

however I will go with B

120pi+160+90pi+120=210pi+280
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Re: geometry - difficult [#permalink]  10 Jun 2008, 07:09
3/4*(2*pi*R + 2*pi*r) + 2*(R + r) -> B
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Re: geometry - difficult [#permalink]  10 Sep 2011, 05:56
1
KUDOS
important thing where i got stuck...
i found this on another site..its really help full.

I feel we are not supposed to take the literal meaning of the term "cord" {lineseg that lies inside the cirlce with its ends lieing on the circle"} [color=#FF4040]as its meaning but as a piece of wire/some material that goes around the 2 circles[/color].

so.........

Since the tangents form squares with the radii.

the total length as tangents = 2*80+2*60 = 280

and the total lenght wound around the circles = 270deg/360deg * 2*pi*80
=120pi

for the second circle similarly 90pi
therfore 210pi+280
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Re: geometry - difficult [#permalink]  18 Sep 2011, 15:20
What is OA and source.
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http://gmatclub.com/forum/massive-collection-of-verbal-questions-sc-rc-and-cr-106195.html#p832142
http://gmatclub.com/forum/1001-ds-questions-file-106193.html#p832133
http://gmatclub.com/forum/gmat-prep-critical-reasoning-collection-106783.html
http://gmatclub.com/forum/how-to-get-6-0-awa-my-guide-64327.html
http://gmatclub.com/forum/how-to-get-6-0-awa-my-guide-64327.html?hilit=chineseburned

Re: geometry - difficult   [#permalink] 18 Sep 2011, 15:20
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