A man drives from home to work at a speed of 50mih The retur

A man drives from home to work at a speed of 50mi/h. The return trip from work to home is traveled at the more leisurely pace of 30 mi/h. What is the man\'s average speed for the round trip?

Solution

We know the man drives to work at 50 mph.
We know he drives home at 30 mph.
We know the distance is the same both ways.
What we do not know are the times involved.
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Let\'s assume he drives 30 miles to and from work.
At 50 mph it takes him 30/50 or .6 of an hour to drive to work. .6*60 = 36 minutes
At 30 mph it takes him 30/30 or 1 hr to drive home = 60 minutes
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So the total elapsed time is 96 minutes to drive 60 miles.
96 minutes = 1.6 hr
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Going back to d=rt
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60 miles = r mph * 1.6 hr = 1.6r
.
Dividing both sides by 1.6
37.5 = r
r = 37.5