Question 792484: A girl goes to her school from her home at 3 km/h and come back from her school at 2 km /h she takes total 5 hourse time then what is the distance between her home and the school?
Answer by Alan3354(69443)   (Show Source):
You can put this solution on YOUR website! A girl goes to her school from her home at 3 km/h and come back from her school at 2 km /h she takes total 5 hourse time then what is the distance between her home and the school?
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Avg speed of a round trip is
2*r1*r2/(r1+r2)
= 2*3*2/(3+2) = 12/5
= 2.4 km/hr
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d = r*t = 2.4*5 = 12 km RT
One way = 6 km
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Avg speed of a round trip is
2*r1*r2/(r1+r2)
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That can be derived easily by picking a distance, eg, 6 km.
It's not possible (or recommended) to remember all the formulas, but this one is similar to parallel resistors, parallel flows, and "parallel" work. It has an additional factor of 2 in the numerator.
2*r1*r2/(r1+r2)
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Parallel resistors is
R1*R2/(R1+R2)
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