If Rachel drives 240 miles at 40 mph, and another 240 at 60 mph, what is her average speed for the entire trip?
Trap answer: you cannot simply average 2 speeds for an average of 50.
Instead, you need to figure out the times:
240/40 = 6 hours on the first leg
240/60 = 4 hours on the second leg
Total hours = 10. Total distance = 480
480 / 10 = 48 mph