SOLUTION: a man drives to his office at 60km/hr and returns home along the same route at 30km/hr. Find the average speed?

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Question 887960: a man drives to his office at 60km/hr and returns home along the same route at 30km/hr. Find the average speed?
Found 2 solutions by josgarithmetic, Alan3354:
Answer by josgarithmetic(39616) About Me  (Show Source):
You can put this solution on YOUR website!
{totalDistance}/{totalTime}

d is distance each way.
RT=D, T=D%2FR.

d%2F60%2Bd%2F30, total time
2d, total distance
highlight%28%282d%29%2F%28d%2F60%2Bd%2F30%29%29, average speed. Simplify that and it will be your finished result.

Answer by Alan3354(69443) About Me  (Show Source):
You can put this solution on YOUR website!
a man drives to his office at 60km/hr and returns home along the same route at 30km/hr. Find the average speed?
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Avg = 2*60*30/(60 + 30) = 3600/90
= 40 km/hr
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It's similar to parallel resistors and parallel flows.
Notice that the distance is not a factor.