They don’t run at the same speed as each other, they run at the same speed with which they ran the first race…

This one is worded oddly, though, because winning a 100 yard race by 10 yards doesn’t really make sense (they should have both run 100 yards). I know what you meant, but it could probably be worded more effectively…

@hatekathy
The assumption is only made in order to show the possible cases. You could just as easily say, “assume that ‘ja’ means no and ‘da’ means yes.” You’ll still come up with the correct
solution, because the answer you get shows which is which.

@nitr0smash
This solution assumes that the rope burns uniformly – that once you fold it in half and light it each half will burn at the same rate. If ‘half 1’ of Rope B takes 50 minutes to burn and ‘half 2’ takes 10 minutes (for example), then even when folded they won’t burn evenly.