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100 points for $49 worth of Veritas practice GMATs FREE VERITAS PRACTICE GMAT EXAMS Earn 10 Points Per Post Earn 10 Points Per Thanks Earn 10 Points Per Upvote ## fraction question ##### This topic has expert replies Senior | Next Rank: 100 Posts Posts: 85 Joined: 08 Dec 2008 ### fraction question by tj123 » Mon Dec 08, 2008 11:32 pm At a speed of 50mph, a certain car uses 1 gallon of gasoline every 30 miles. If the car starts with a full 12 gallon tank of gasoline and travels for 5 hours at 50 mph, the amount of gasoline used would be what fraction of a full tank? I chose 2/3. The answer is 25/36 Please explain how to get the answer. Master | Next Rank: 500 Posts Posts: 145 Joined: 29 Sep 2008 Thanked: 13 times by mental » Mon Dec 08, 2008 11:47 pm At a speed of 50mph, a certain car uses 1 gallon of gasoline every 30 miles. travels for 5 hours at 50 mph distance travelled: 5*50 = 250 miles gas used: 250/30 = 25/3 gallon = x the amount of gasoline used would be what fraction of a full tank? x is what fraction of 12? x/12 = (25/3)/12 = 25/36 Senior | Next Rank: 100 Posts Posts: 85 Joined: 08 Dec 2008 by tj123 » Tue Dec 09, 2008 11:16 am i did 250/30 = 8.33 then i did 8/12 which = 2/3 why is this way wrong? i used the same method as you used? ### GMAT/MBA Expert GMAT Instructor Posts: 3225 Joined: 08 Jan 2008 Location: Toronto Thanked: 1710 times Followed by:613 members GMAT Score:800 by Stuart@KaplanGMAT » Tue Dec 09, 2008 2:15 pm tj123 wrote:i did 250/30 = 8.33 then i did 8/12 which = 2/3 why is this way wrong? i used the same method as you used? Because you did 8/12 instead of 8.33/12. Let's convert 8.33 to a fraction to make the math easier. 8.33 = 8 and 1/3 = 25/3 (25/3)/12 = (25/3)*(1/12) = 25/36. 25/36 is only 1/36 more than 2/3. When the answers are that close together, it's not safe to round off. Stuart Kovinsky | Kaplan GMAT Faculty | Toronto Kaplan Exclusive: The Official Test Day Experience | Ready to Take a Free Practice Test? | Kaplan/Beat the GMAT Member Discount BTG100 for$100 off a full course

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by niraj_a » Tue Dec 09, 2008 8:05 pm
stuart,

this was certaonly helpful, but would a nitty-gritty on these lines show up on the real GMAT?

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by canuckclint » Tue Dec 09, 2008 10:45 pm
niraj_a wrote:stuart,

this was certaonly helpful, but would a nitty-gritty on these lines show up on the real GMAT?
GMAT is multiple choice.
If they do not say to approximate then do not.

They will provide a fractional answer like 25/36 and you can chose that.
They will not check your work.

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by niraj_a » Wed Dec 10, 2008 4:59 am
canuck,

2/3 is a fraction too right? no issues, i'll look out for the word 'approximate' and then be sure to choose the most BS answer that's close to my calculated answer.

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