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?
(In reply to
re: solution, maybe by Charlie)
In fact, this solution remains the same even if the figure had been a square rather than a circle, as the probability is zero that any chosen point is a corner.

Posted by Charlie
on 20090512 11:10:59 