question: A car is on a road trip and drives 60 mph for 2 hours, and then 30 mph for 1 hour. What is the car's average speed in mph during this trip?
answer: The car drives 60*2=<<60*2=120>>120 miles for 2 hours.
  The car drives 30*1=<<30*1=30>>30 miles for 1 hour.
  It drives a total of 120+30=<<120+30=150>>150 miles.
  Let S be the average speed, M be the number of miles, and H the number of hours spent driving.
  Then we have, S=M/H, so, S=150 miles/3 hours = <<150/3=50>>50 mph
  #### 50