conversations.from: human
conversations.value: Some friends went hiking for 3.5 hours. They traveled 21 kilometers in that time. Birgit was 4 minutes/km faster than the average time. If Birgit kept the same pace, how many minutes would it take her to go 8 kilometers?
  Give me a detailed solution.
conversations.from: assistant
conversations.value: Minutes spent hiking = 3.5*60 = 210 minutes
  Average speed = 210 minutes/ 21 km = 10 minutes/km
  Birgit is 4 minutes/km faster = 10 - 4 = 6 min/km
  It would take 6*8 = 48 minutes to go 8 km
  Birgit would take 48 minutes to travel 8 kilometers.