Average speed problem?

Question

Your plan was to be on the road at 9am but you did not leave your garage until 10am. You drove with the cruise control set at 75mph until stopping at noon. What is your average speed from 9am to noon?

The answer says its 2.4mph, but i keep getting 37.5 mph. can someone explain this?

Answer 1

Distance = speed * time

From 9 am to 10 am you were not driving at all. The total distance covered = 0 miles.
From 10 am to 12 pm (noon), you were driving at a rate of 75 miles per hour [for 2 hours]. The total distance covered here was 150 miles.

The grand total distance driven from 9 am to 12 pm was 0 + 150 miles = 150 miles.
The time you are taking the average over is 3 hours.

Average speed = total distance traveled / total time
Average speed = 150 miles / 3 hours
Average speed = 50 miles per hour

Answer 2

The answer is 50mph

If you travel at 75mph for two hours you've travelled 150 miles
150miles divided by 3 hours = 50 miles per hour