Question 1189462: Sam drove to work at an average speed of 50 miles per hour from her house and then returned along the same route at an average speed of 40 miles per hour. If the entire trip took her 2.25 hours, what is the entire distance, in miles, for the round trip?
Answer by Alan3354(69443)   (Show Source):
You can put this solution on YOUR website! Sam drove to work at an average speed of 50 miles per hour from her house and then returned along the same route at an average speed of 40 miles per hour. If the entire trip took her 2.25 hours, what is the entire distance, in miles, for the round trip?
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Avg speed of the round trip is 2*50*40/(50+40) = 400/9 mi/hr
d = (400/9)*2.25 = 100 miles (50 miles each way)
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The formula for average speed of a round trip (or of equal parts) is
2*v1*v2/(v1 + v2)
Similar to parallel work, parallel flows, parallel resistance.
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