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# You travel from home to work at 50 miles per hour. As soon

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Manager
Joined: 22 May 2007
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You travel from home to work at 50 miles per hour. As soon [#permalink]  03 Jul 2007, 13:57
You travel from home to work at 50 miles per hour. As soon as you get there you realize that you have forgotten something. You rush back right away to take it from your home at 100 mph. What was your average speed for the entire trip?
Manager
Joined: 18 Apr 2007
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I know there are different ways to figure out the average speed...can you please post an explanation of how you got your answer? Thanks!
Manager
Joined: 22 May 2007
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Total distance over total time. The distance in this case can be anything.

I pick numbers that are easy to work with. Let's say that from home to office is 100 miles. It took me 2 hours to make it to the office (at 50 mph). It took me 1 hours to make it back (at 100 mph). Total distance covered - 100+ 100 = 200 miles. Total time - 2+1 = 3 hours.

200/3 = 66.66666.

Many people will go for the usual trap - (100 + 50)/2 = 75 average speed.
Note that if you travel for 3 hours @ 75 mph, you will cover 225 miles!
Manager
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Manager
Joined: 24 Jun 2006
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for "going-return" problem check out that formula for average speed
average speed= 2V1V2/(V1+V2)= 2*50*100/(100+50)= 66.2/3
and save 1 minute on GMAT
Manager
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You're awesome boubi! Thanks! What a time saver!
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