<PRE><B>Question 697316</B>
Starting at home, Stephanie traveled uphill to the gift store for 30 minutes at just 10 mph. She then traveled back home along the same path downhill at a speed of 30 mph.

What is her average speed for the entire trip from home to the gift store and back?
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avg = 2*10*30/(10+30)
= 15 mi/hr regardless of distance
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The long way:
30 mins (1/2 hr) at 10 mi/hr --&gt; d = 5 miles
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5 miles @ 30 mi/hr = 1/6 hour
Total time = 2/3 hour
Total distance = 10 miles
r = 10/(2/3) = 15 mi/hr
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