DAY 246
An airplane flies 3,000 miles from LA to NY at 600 mph thanks to a strong tailwind from the jet stream. On the return trip the tailwind is now a headwind, and the plane averages only 400 mph for the return trip. What is the average speed of the plane for the entire round-trip flight?

Answer:

480 mph.............Time is distance divided by speed. The flight from LA to NY took 5 hours. The return flight took 7.5 hours. Speed is distance divided by time. The average speed for the round-trip flight is 6,000 miles divided by 12.5 hours.