math
posted by donna .
a truck driver traveled at an average speed of 48 miles per hour on a 100mile trip to pick up a load of freight. On the return trip with the truck fully loaded,the average speed was 40 miles per hour. Find the average speed for the round trip.

time for first trip = 100/48 hours = 25/12 hrs
time for return trip = 100/40 = 5/2 hours
total time = 5/2 + 25/12 hours = 55/12 hrs
avg speed = total distance / total time
= 200/(55/12) = 43.64 mph