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 = 
<gadget id="calculator">3.5*60</gadget>
<output>210</output>
210 minutes.
Average speed = 210 minutes/ 21 km = 
<gadget id="calculator">210/21</gadget>
<output>10</output>
10 minutes/km.
Birgit is 4 minutes/km faster = 10 - 4 = 6 min/km.
It would take 6*8 = 
<gadget id="calculator">6*8</gadget>
<output>48</output>
48 minutes to go 8 km.
Birgit would take 48 minutes to travel 8 kilometers.

<result>48</result>