conversations.from: human
conversations.value: I would love to understand how to solve this problem: A man drives 60 mph for 3 hours.  How fast would he have to drive over the next 2 hours to get an average speed of 70 mph?
  Can you explain?
conversations.from: assistant
conversations.value: To have an average speed of 70 mph over 5 hours he needs to travel 70*5=350 miles.
  He drove 60*3=180 miles in the first 3 hours
  He needs to travel another 350-180=170 miles over the next 2 hours.
  His speed needs to be 170/2=85 mph