To average 30 mph, you would have to cover the 2-mile course in 4 minutes. At 15 mph, you would take the entire 4 minutes to travel the first mile; therefore you would have to cover the second (downhill) mile instantaneously.
Teleportation, anyone?
Zeko
Here's one for you:
Which is heavier, a pound of gold or a pound of feathers? Explain your answer.
FReegards!