I can appreciate if someone doesn't (or if most people don't, even) see the fun in this, sure.
> Considering the first mile would need to have been faster than 23mph
That said, note that it's not just the up-leg's average speed that's been provided (15 mph), but also the distance as you say (1 mile). If you explore the error term for both of these, you'll see that it's not necessary to go at the ludicrously high speed of 23 mph after all. """15 mph""" (15.444... mph) will do just fine.
If you go as far as assuming the mile distance is wrong then the entire question is pointless, maybe they've already travelled more than two miles and they need to go backwards to average 30mph! At that point literally any number is just as correct as 41 is...
It does allow for making any number between 40.833546516585657030783661635542 (exact) and ∞ work, 41 just being the lowest whole number that works. Travelling backwards, being arbitrarily wrong, or any arbitrary number working doesn't fit these new constraints still, however.
> Considering the first mile would need to have been faster than 23mph
That said, note that it's not just the up-leg's average speed that's been provided (15 mph), but also the distance as you say (1 mile). If you explore the error term for both of these, you'll see that it's not necessary to go at the ludicrously high speed of 23 mph after all. """15 mph""" (15.444... mph) will do just fine.