SOLUTION: You travel up a hill at 10mph. You travel down the hill at 30mph. What was your average speed?

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Question 728685: You travel up a hill at 10mph. You travel down the hill at 30mph. What was your average speed?
Answer by josmiceli(19441) About Me  (Show Source):
You can put this solution on YOUR website!
Average speed is ( total distance ) /( total time )
Going up:
+d+=+10t%5B1%5D+
+t%5B1%5D+=+d+%2F+10+
Going down:
+d+=+30t%5B2%5D+
+t%5B2%5D+=+d+%2F+30+
-----------------
+2d+%2F+%28+t%5B1%5D+%2B+t%5B2%5D+%29+=+2d+%2F+%28+d%2F10+%2B+d%2F30+%29+
++2d+%2F+%28+d%2F10+%2B+d%2F30+%29+=+2+%2F+%28+1%2F10+%2B+1%2F30+%29+
+2+%2F+%28+3%2F30+%2B+1%2F30+%29+
+2+%2F+%28+4%2F30+%29+=+60%2F4+
+60%2F4+=+15+
The average speed is 15 mi/hr