OG - PS - #129

[mrkamal]

Hi,
I'm confused by PS Q#129, pg 169 of the 11th Ed guide.
It asks about rounding off miles and gallons of gas and I don't understand how the number of miles can be between 284 - 295 when they were rounded to the nearest 10 miles to 290 (as it says is the question). I would have thought 286 - 294 would round up or down to 290, since I thought 284 would round down to 280 and 295 up to 300. The same principle is confusing me with the gallons of gas. If they were rounded to the nearest gallon at 12, how could the range be 11.4 - 12.5?
Thanks,
AK

[dbernst]

Mr. Kamal,

Now I'm confused!!! In my book I don't see any 284s or 11.4s. Perhaps your book has a misprint? In the future, please include the entire problem and its answer choices in your posts. This will help clarify any discrepancies and will also allow other students to learn from your posts.

In this case, I will reproduce the problem at written in my book.

Q: 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

A) 290/12.5 to 290/11.5

B) 295/12 to 285/11.5

C) 285/12 to 295/12

D) 285/12.5 to 295/11.5

E) 205/12.5 to 285/11.5

Explanation: Since her mileage was 290 rounded to the nearest 10, Cindy must have traveled between 285 and 295 miles. Moreover, since her gasoline usage was 12 gallons rounded to the nearest gallon, she must have used between 11.5 and 12.5 gallons.

At her worst miles per gallon, she would have traveled the fewest miles (285) on the greatest number of gallons (12.5), and at her best miles per gallon she would have traveled the greatest number of miles (295) on the fewest gallons (11.5).

The correct answer is D!

Hi,
I'm confused by PS Q#129, pg 169 of the 11th Ed guide.
It asks about rounding off miles and gallons of gas and I don't understand how the number of miles can be between 284 - 295 when they were rounded to the nearest 10 miles to 290 (as it says is the question). I would have thought 286 - 294 would round up or down to 290, since I thought 284 would round down to 280 and 295 up to 300. The same principle is confusing me with the gallons of gas. If they were rounded to the nearest gallon at 12, how could the range be 11.4 - 12.5?
Thanks,
AK

[GMAT 5/18]

This one is confusing a lot of us! I haven't looked at the actual question in the book, but I have a question.

Dan,

Wouldn't 295 rounded to the nearest 10 be 300? I would have thought that since her mileage was 290 rounded to the nearest 10, Cindy must have traveled between 285 and 294 miles, not 295 miles.

Thanks!

[bshirley]

Dan,

I have the same question about rounding off as previously noted. The question in the OG pg. 169 #129 is:

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

(A) 290/12.5 and 290/11.4
(B) 295/12 and 284/11.4
(C) 284/12 and 295/12
(D) 284/12.5 and 295/11.4
(E) 295/12.5 and 284/11.4

None of these answers seem to make sense. Shouldn't the answer be lowest number of miles per gallon = 285/12.4 and highest number of miles per gallon = 294/11.5?

Thanks,

Ben

[GMATPaduan]

BShirley - the issue is that the question asks for the range,i.e. The actual miles must have been BETWEEN.....and your response includes the actual answer to the question..

To clarify....if the answer is 2<x<5, x is neither equal to 2 nor 5......x is greater than 2, but less than 5

[mrkamal]

I understand now, based on that last response. I was including the range numbers in my calculations...
Thanks,
AK

p.s. It seems this problem should be considered 600+ based on that "trap" in the answer choices. It definitely got me!

[dbernst]

I'm glad everybody seems clear on this one. As for the difficulty level, I would estimate this problem to be well above 600. Not only do you have to read carefully (remember, "The Math is the Verbal") and understand the rounding process, but you also have to recognize that the worst possible mileage would happen with fewest miles traveled and the greatest gasoline consumption, and the best possible mileage would be the opposite.

-dan

ps. I intentionally included a not only...but also idiom in my response, just to make sure you guys and gals don't forget about verbal :)

I understand now, based on that last response. I was including the range numbers in my calculations...
Thanks,
AK

p.s. It seems this problem should be considered 600+ based on that "trap" in the answer choices. It definitely got me!