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?
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
Just realized that I did this same question back in 2007, (and got the same answer)
http://www.jiskha.com/display.cgi?id=1195533760
To find the average speed for the round trip, we need to calculate the total time taken for the trip and divide it by the total distance traveled. Let's break it down step by step:
Step 1: Calculate the time taken for the outbound trip.
The distance covered on the outbound trip is 200 miles, and the average speed was 55 miles per hour. We can apply the formula: Time = Distance / Speed to find out the time taken.
Time (outbound trip) = 200 miles / 55 miles per hour
Step 2: Calculate the time taken for the return trip.
The distance covered on the return trip is also 200 miles, but the average speed was 40 miles per hour.
Time (return trip) = 200 miles / 40 miles per hour
Step 3: Find the total time for the round trip.
The total time for the round trip is the sum of the time taken for the outbound and return trips.
Total time = Time (outbound trip) + Time (return trip)
Step 4: Calculate the average speed for the round trip.
To find the average speed, we divide the total distance (400 miles) by the total time taken for the round trip.
Average speed = Total distance / Total time
Now, let's calculate the individual values:
Time (outbound trip) = 200 miles / 55 miles per hour = 3.636 hours
Time (return trip) = 200 miles / 40 miles per hour = 5 hours
Total time = 3.636 hours + 5 hours = 8.636 hours
Average speed = 400 miles / 8.636 hours
Therefore, the average speed for the round trip is approximately 46.29 miles per hour.