SOLUTION: 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 ro

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Question 249429: 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?
(I know the answer is not 40mi/h though)
Answer by oberobic(2304) About Me  (Show Source):
You can put this solution on YOUR website!
We know the basic formula for distance problems is: d = rt, where d=distance, r=rate, t=time.
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.
.
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
.
So the total elapsed time is 96 minutes to drive 60 miles.
96 minutes = 1.6 hr
.
Going back to d=rt
.
60 miles = r mph * 1.6 hr = 1.6r
.
Dividing both sides by 1.6
37.5 = r
r = 37.5
.
Checking our work...
How far will the car go in 1.6 hr at 37.5 mph?
60 miles
OK.