SOLUTION: a woman jogs 2 km at 8km/h and then walks for 2 km at 6 km/h. what is her average speed for entire trip?

Question 570853: a woman jogs 2 km at 8km/h and then walks for 2 km at 6 km/h. what is her average speed for entire trip?
Found 2 solutions by josmiceli, Alan3354:
Answer by josmiceli(19441) (Show Source): You can put this solution on YOUR website!
average speed = ( distance traveled ) / ( time to travel the distance )
given:

hr
and

hr
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Ave speed =

km/hr
Answer by Alan3354(69443) (Show Source): You can put this solution on YOUR website!
a woman jogs 2 km at 8km/h and then walks for 2 km at 6 km/h. what is her average speed for entire trip?
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The avg speed of a round-trip (or of equal distances) is
2*r1*r2/(r1 + r2)
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This is similar to parallel resistors and parallel flows, and other problems, but with a 2 in the numerator.
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2*8*6/(8 + 6) = 96/14
= 48/7 km/hr
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Notice that it's less than the avg of 8 and 6, because more time is spent going 6 km/hr than going 8 km/hr over the same distance.
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This is the basis of the Michelson-Morley experiment in the 1840's that showed there is no effect from "the ether" on the speed of light, which disproved the existence of the ether. Ether joined phlogiston on the pile of things that don't exist.
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