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$X_1, X_2,\ldots,X_9$ are nine points on the circumference
of circle $O$. Line segments are drawn connecting each pair of points.

How many line segments are drawn?

Guest Mar 29, 2015

Best Answer 

 #1
avatar+26412 
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Each point is connected to 8 others, so, 9*8.  But this counts each line twice, so the number of lines is 9*8/2 = 36

.

Alan  Mar 29, 2015
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1+0 Answers

 #1
avatar+26412 
+10
Best Answer

Each point is connected to 8 others, so, 9*8.  But this counts each line twice, so the number of lines is 9*8/2 = 36

.

Alan  Mar 29, 2015

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