I was walking along the road one day when I spied a cord of some sort lying in my path. From my vantage point, as I was approaching the cord, I could not tell if it was knotted or not.
What is the probability that the cord was knotted?
Looking at the 8 different configurations: described as whether the end
closes to A passes under or over at intersections 1, 2 and 3
OOO: no knot
OOU: no knot
OUO: knot
OUU: no knot
UOO: no knot
UOU: knot
UUO: no knot
UUU: no knot
Therefore is a 2 in 8, or 25% chance that the rope is knotted. It
seems like there should be an intuitive answer, but I brute-forced it.