OG Car X traveled north

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AbeNeedsAnswers: Master | Next Rank: 500 Posts; Posts: 394; Joined: Sun Jul 02, 2017 10:59 am; Thanked: 1 times; Followed by:5 members

OG Car X traveled north

by AbeNeedsAnswers » Wed Aug 16, 2017 6:24 pm

During a certain time period, Car X traveled north along a straight road at a constant rate of 1 mile per minute and used fuel at a constant rate of 5 gallons every 2 hours. During this time period, if Car X used exactly 3.75 gallons of fuel, how many miles did Car X travel?

A. 36
B. 37.5
C. 40
D. 80
E. 90

E

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Source: Beat The GMAT — Problem Solving | Wed Aug 16, 2017 6:24 pm

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by [email protected] » Thu Aug 17, 2017 10:49 am

Hi AbeNeedsAnswers,

We're told several facts about a car driving on a straight road:
1) The car drives at 1 mile/minute
2) The car uses 5 gallons of fuel every 2 hours
3) The car used exactly 3.75 gallons of fuel

We're asked to find the number of miles that the car traveled. This is essentially a 'rate' question - and you can do the 'math' in a few different ways (depending on how you want to organize the information.

We know that 5 gallons of fuel is used every 2 hours, so we can figure out how long 3.75 gallons of fuel will last:

(3.75/5)(2 hours)

7.5/5 hours = 1.5 hours = (1.5)(60 minutes) = 90 minutes

Since the care traveled 1 mile/minute, and the fuel lasted for 90 minutes, the car traveled 90 miles.

Final Answer: E

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Rich

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Matt@VeritasPrep: GMAT Instructor; Posts: 2630; Joined: Wed Sep 12, 2012 3:32 pm; Location: East Bay all the way; Thanked: 625 times; Followed by:119 members; GMAT Score:780

by Matt@VeritasPrep » Fri Aug 18, 2017 1:56 pm

The car traveled for 3.75/5, or 3/4 of 2 hours, at a rate of 60mph, so the car traveled (3/4) * 120, or 90 miles.

(That 2 hours part is easy to overlook: I guess having 45 as an answer was too evil even for the GMAT!)

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Jeff@TargetTestPrep: GMAT Instructor; Posts: 1462; Joined: Thu Apr 09, 2015 9:34 am; Location: New York, NY; Thanked: 39 times; Followed by:22 members

by Jeff@TargetTestPrep » Mon Aug 21, 2017 3:34 pm

AbeNeedsAnswers wrote:During a certain time period, Car X traveled north along a straight road at a constant rate of 1 mile per minute and used fuel at a constant rate of 5 gallons every 2 hours. During this time period, if Car X used exactly 3.75 gallons of fuel, how many miles did Car X travel?

A. 36
B. 37.5
C. 40
D. 80
E. 90

E

Since the car has a constant rate of 1 mile per minute, we can let r = the rate of the car in miles per hour and create the following equation:

1/1 = x/60

x = 60 mph

Since the car uses 5 gallons of fuel every 2 hours, we can let x = the number of hours driven when the car uses 3.75 gallons of fuel and create the following proportion:

5/2 = 3.75/x

5x = 7.5

x = 1.5 hours

We know that the rate of the car is 60 mph and the car has driven 1.5 hours; thus, the distance driven is 60 x 1.5 = 90 miles.

Answer: E

Jeffrey Miller
Head of GMAT Instruction
[email protected]