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Source: Official Guide for the GMAT 13th Ed. Problem Solving; #79 Official Guide for the GMAT 2015 14th Ed. Problem Solving; #79


After driving to a riverfront parking lot,

After driving to a riverfront parking lot, Bob plans to run south along the river, turn around, and return to the parking lot, running north along the same path. After running 3.25 miles south, he decides to run for only 50 minutes more. If Bob runs at a constant rate of 8 minutes per mile, how many miles farther south can he run and still be able to return to the parking lot in 50 minutes?

2 Explanations


Sean Gregory

First find out how much time he spent running 3.25 miles.
3.25*8 = 26 minutes. He then decided to run an additional 50 minutes equaling total 76 minutes running. We know he has to run back 3.25 miles he just ran. So we know 26+26= 52 minutes spent running the known distance leaving 76 - 52 = 24 minutes left to run. To find out the distance we divide 24/8 = 3 miles left to run. But we only want to know how far he ran before he had to turn back So divide 3/2 = 1.5 miles.

Mar 10, 2015 • Comment

Jonathan , Magoosh Tutor

Hi Sean,
That's a correct and innovative alternate approach. Nice job :)

Mar 16, 2015 • Reply

Merlin Alex

How is 3.25*8 = 26 minutes? Isnt time = Distance/Rate?

Jul 24, 2017 • Reply

Cydney Seigerman, Magoosh Tutor

Happy to clarify :)

We get "minutes" when we carry out that product because of the units associated with the two values. We are multiplying 3.25 miles x 8 minutes/mile. When we multiply the two terms together, the unit "miles" cancel out, as we have miles in the numerator of one term and in the denominator of the other. And this leaves us with "minutes" as the unit of the product!

I hope this clears up your doubt!

Jul 30, 2017 • Reply


Gravatar Mike McGarry, Magoosh Tutor

Dec 27, 2013 • Comment

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