SOLUTION: What is the average speed of a cyclist who bikes up a hill at 6mph but then bikes back along the same path down the hill at 12 mph? Also how did you get the answer? Thank you.

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Question 803194: What is the average speed of a cyclist who bikes up a hill at 6mph but then bikes back along the same path down the hill at 12 mph? Also how did you get the answer? Thank you.
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Average speed is always ( total distance ) / ( total time )
Let +d+ = the one-way distance traveled
--------------
Time in hrs going up the hill:
+d+%2F+6+
Time in hrs going down the hill:
+d+%2F+12+
--------------
The total distance traveled is +2d+
The cyclist's average speed is:
+2d+%2F+%28+d%2F6+%2B+d%2F12+%29+
+2d+%2F+%28+d%2A%28+1%2F6+%2B+12%2F12+%29+%29+
+2+%2F+%28+1%2F6+%2B+1%2F12+%29+
+2+%2F+%28+2%2F12+%2B+1%2F12+%29+
+2+%2F+%28+3%2F12+%29+
+%28+12%2F3+%29%2A2+
+4%2A2+=+8+
The cyclist's average speed is:8 mi/hr