A truck driver traveled at an average speed of 55 miles per hour on a 200-mile trip pick up a load of freight. On the return trip (with the truck fully loaded), the average speed was 40 miles per hour. What was the average speed for the round trip?

Answer 1

time for 1st trip = 200/55 = 40/11 hrs
time return trip = 200/40 = 5 hrs

avg speed = 400/(5+40/11) = 880/19 mph
or appr 46.3 mph

Answer 2

Just realized that I did this same question back in 2007, (and got the same answer)

http://www.jiskha.com/display.cgi?id=1195533760