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?
Minutes spent hiking = 3.5*60 = <<3.5*60=210>>210 minutes
Average speed = 210 minutes/ 21 km = <<210/21=10>>10 minutes/km
Birgit is 4 minutes/km faster = 10 - 4 = 6 min/km
It would take 6*8 = <<6*8=48>>48 minutes to go 8 km
Birgit would take 48 minutes to travel 8 kilometers.
#### 48