Lol, I am also intrigued by maths problems especially those involving statistics/probabilities. So I also did the problems, and this is my answer
Probability of one team not getting through detour
= (33/38)^4 X 100%
= (33x33x33x33) / (38x38x38x38) X 100%
Thus probability of one team getting thru detour
Which is actually the same method as pineapple's one, just that i took it as 38 numbers and not 37 numbers.
Thus probability of ALL 4 teams getting through detour
= (43.13/100)^4 X 100%
Hope i am correct on this one! Perhaps someone can verify this? Anyway, 3.46% seems incredibly small eh. And yet, all 4 teams managed to clear that detour. 1) My percentages are wrong 2)Sometimes, probabilities does not mean anything! Anything can happen in life!
Haha, anyway, on that very spot of time, I guess I would have gone to do the Zips, since on my first impression, I thought clearing the Chips detour requires lots of luck.