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Random chord problem (Posted on 2009-05-11) Difficulty: 1 of 5
Pick two points at random on a circle and draw the chord connecting them.

Pick two more points and connect them with a second chord.

What is the probability that these chords intersect?

See The Solution Submitted by Jer    
Rating: 3.0000 (1 votes)

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Solution solution, maybe | Comment 8 of 17 |

This is possibly too easy, but instead of thinking of it as 2 points chosen and then two more points chosen, let's just think of it as 4 points chosen.  Once I have four points, there are only three ways to draw 4 chords: one way is an x, and the other two are semi-parallel segments. 

Well...then, the probability that the chords intersect is 1/3.

I've been chewing on this one all afternoon, and this answer seems to simplistic, but--as was pointed out in the comments--it is difficulty 1. 


  Posted by Stephanie on 2009-05-11 19:35:23
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