Question 626063
Linda hiked up a mountain trail and camped overnight at the top. The next day she returned down the same trail. Her average rate traveling uphill was  kilometers per hour and her average rate downhill was  kilometers per hour. If she spent a total of  hours hiking, how long was the trail? 
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No numbers are given.
Avg spd for a round-trip is
2*r1*r2/(r1 + r2), r1 & r2 are the speeds
It's similar to parallel resistors, flow problems, etc, but times 2.