Question

Jimmy made a trip to the ferry office and back. The trip there took two hours and the trip back took three hours. He averaged 20 mph faster on the trip there than on the return trip. Find Jimmy's average speed on the outbound trip.

Answer 1

60 mph

Explanation:

We don't know how far Jimmy drives in each direction. Let this distance be d. Then, d = rate * time, and d = r(2 hours) (where r represents his speed while driving to the ferry).

But it's also true that d = (r - 20 mph)(3 hours).

Equating d = r(2 hours) and d = (r - 20 mph)(3 hours), we get:

r(2) = (r - 20)(3), or 2r = 3r - 60.

Subtracting 2r from both sides yields 0 = r - 60, so that r = 60 mph.

Jimmy averaged 60 mph on the outbound trip.