This problem is from Problem Solving Strategies - Crossing the River with Dogs and Other Mathematical Adventures by Ken Johnson and Ted Herr.
I decided to draw a picture from the segment of $90$ ft to $100$ ft of the race (the wall where they turn around). I chose to start at $90$ ft because both two and three go into 90 evenly, so neither Roo or Tigger are in the middle of a jump at that time.
Thus, at the $96$ foot mark, both Roo and Tigger are at the same spot. But, at the $98$ foot mark, Roo is about to jump to the $100$ ft mark and Tigger is mid-jump en route to the $99$ ft mark. So, when Roo jumps, he is at the $100$ ft mark and ready to turn around, while Tigger is on the $102$ ft mark and then waiting to turn back around.
I am having trouble trying to figure out how much Roo wins by then exactly. It's hard to tell from my picture, but I believe it would be $2$ feet. Is that correct, or does Roo possibly win by more? Any help would be appreciated.