Clyde drove 30 miles in 20 minutes and then drove an additional 10 miles in 10 minutes. What is the average speed for the entire trip?

Average speed = (total distance covered) / (time to cover the distance)

Clyde's total distance covered = (30 miles + 10 miles) = 40 miles

Time to cover the distance = (20 minutes + 10 minutes) = 30 minutes

Average speed = (40 miles) / (30 minutes) = 4/3 miles per minute = 80 mph