uphill at a rate of 2.5 mi/h from the base of a 6-mi trail. At the same time, Edwin walks downhill at a rate of 3.5 mi/h from the top of the trail. How many hours pass before they meet on the trail?

After 1 hour they meet.

Explanation:

Distance between them = 6 miles

Speed of uphill person = 2.5 miles per hour

Speed of downhill person = 3.5 miles per hour

Relative velocity = 2.5 - (-3.5) = 6 miles per hour

We know

Displacement = Velocity x Time

6 = 6 x Time taken

Time taken = 1 hour

After 1 hour they meet.