SOLUTION: if 15 points are arranged on a circle. How many lines are needed to join every point to every other point once?

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Question 254228: if 15 points are arranged on a circle. How many lines are needed to join every point to every other point once?
Answer by Edwin McCravy(20055) About Me  (Show Source):
You can put this solution on YOUR website!

Order is not important because line segment (chord) AB 
and line segment BA are the same line segment.  so it's

"15 points Choose 2"

15C2+=+15%21%2F%282%2113%21%29+=+%2815%2A14%29%2F%282%2A1%29+=+15%2A7=105

Edwin