Question 712328
A car travels along a straight line at a constant speed of 62.5 mi/h for a distance d and then another distance d in the same direction at another constant speed. The average velocity for the entire trip is 32.5 mi/h. 
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1st leg DATA:
distance = d miles ; rate = 62.5 mph ; time = d/r = d/62.5 hours
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2nd leg DATA:
distance = d miles ; rate = r mph ; time = d/r hrs
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Equation:
average speed = (total distance)/(total time) = (2d miles)/[(d/62.5)+(d/r)]
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(2d)/[rd+62.5d)/(62.5r)] = 32.5 mph
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(125rd = 32.5[rd+62.5d]
125rd = 32.5rd + 2031.25d
92.5rd - 2031.25d = 0
etc.
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Cheers,
Stan H.