conversations.from: human
conversations.value: I would love to understand how to solve this problem: 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?
  Can you explain?
conversations.from: assistant
conversations.value: The car drives 60*2=120 miles for 2 hours.
  The car drives 30*1=30 miles for 1 hour.
  It drives a total of 120+30=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 = 50 mph