BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

OG 129

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
User avatar
Master | Next Rank: 500 Posts
Posts: 355
Joined: Thu Feb 19, 2009 12:42 pm
Thanked: 2 times
Followed by:1 members

OG 129

by vineetbatra » Sat May 30, 2009 1:41 pm
On a recent trip, cindy drove her car 290 miles rounded to the nearest 10 miles, and used 12 gallons of gasoline, rounded to the nearest gallon. The actual number of miles per gallon that cindy's car got on this trip must have been between

284/12.5 and 295/11.4

The explanation says that, since the miles are rounded to the nearest 10 miles, they can range anywhere between 284 to 295. My question is shouldn't it be 286 - 294 because 284 is closer to 280 and not 290, similarly 295 is closer to 300.

I am a little confused, please advice?
Top
Source: — Problem Solving |
Master | Next Rank: 500 Posts
Posts: 103
Joined: Mon May 18, 2009 9:47 am
Thanked: 19 times

by raleigh » Sat May 30, 2009 2:32 pm
Initially, I took 285mi-294mi and 11.5g to 12.4g which leads to the range of 285/12.4 - 294/11.5.

Luckily, D is very close to that so I would have chosen correctly. The big thing here is that they say BETWEEN. Between is exclusive. ie if x is between 0 and 1, then 0 < x < 1.

So 294 is not the maximum number of miles. 294.9 mi gets rounded to 290. 294.99, 294.999, 294.9999,... all get rounded to 290.

Similarly, 285.1 gets rounded to 290. 285.01, 285.001, 285.0001,... all get rounded to 290.

So the number of miles traveled is between 285 and 295.

You can make the same argument for gallons of gasoline to see that the gallons of gasoline are between 11.5 and 12.5. I hope this helps. It is really just trying to confuse you with the definition of between.
Top
User avatar
Master | Next Rank: 500 Posts
Posts: 355
Joined: Thu Feb 19, 2009 12:42 pm
Thanked: 2 times
Followed by:1 members

Thanks

by vineetbatra » Sat May 30, 2009 6:30 pm
Thanks for the reply... I guess pick the closest evil...
Top
Master | Next Rank: 500 Posts
Posts: 119
Joined: Tue Jan 20, 2009 10:16 pm
Thanked: 9 times
GMAT Score:730

by mikeCoolBoy » Sun May 31, 2009 7:14 am
you are ask for an interval that contains the possible values for number of miles per gallon. Let's say X <= number of miles per gallon <=Y.

Now you have to find X and Y.
X should be the smallest possible value while Y should be the biggest possible value according to the restrictions.

Both values X and Y are fractions. We want to minimize X and maximize Y.

To minimize a fraction is to minimize the numerator and maximize the denominator.

the minimum value for the numerator among the options is 284 and the maximum number of the denominator among the options is 12.5 so
X =284/12.5


To maximize a fraction is to maximize the numerator and minimize the numerator.
Maximum value for the numerator is 295 and the minimum value for the denominator is 11.4 so
Y = 295/11.4

D is the correct answer.
Top
Post new topic Post Reply
• Page 1 of 1