Yesterday, Nan parked her car at a certain parking garage

Question

Yesterday Nan parked her car at a certain parking garage that charges more for the first hour than for each additional hour. If Nan’s total parking charge at the garage yesterday was $3.75, for how many hours of parking was she charged?

(1) Parking charges at the garage are $0.75 for the first hour and $0.50 for each additional hour or fraction of an hour.
(2) If the charge for the first hour had been $1.00, Nan’s total parking charge would have been $4.00.

Hi,
Posting this OG question here for discussion. I don't quite agree with the OA due to some lines in the question which I think the explanation overlooked. ( Or I read too deeply into it). Anyway, here it is:

Yesterday, Nan parked her car at a certain parking garage that charges more for the first hour than for each additional hour. If Nan's total parking charge at the garage yesterday was $3.75, for how many hours of parking was she charged?

(1) Parking charges at the garage are $0.75 for the first hour and $0.50 for  each additional hour  or  fraction of an hour.

So for the first hour--> $0.75
Each additional hour --> $0.50
We've met the question's statement "charges more for the first hour than each additional hour", but that's not important.

Since for the first hour it's $0.75, so $3.00 must be incurred by the number of hours parked after the first hour. But we are told that $0.50 is charged for each additional hour OR fraction of an hour, so we can't tell if she parked for 3.00/0.50 = 6 hours, or 5.5 hours with the last fraction of an hour (0.5 in this case) still incurring a 50cents charge.
So statement 1 should be insufficient.

(2) If the charge for the first hour had been $1.00, Nan's total parking charge would have been $4.00.

Not sufficient as we're not told the hourly rate after the first hour.

Combining (1) and (2) still does not answer the niggly question of whether she parked fraction or whole hours. So I picked (E) which the Oa disagrees with.

What do you guys think ?

Alex_NL · Accepted Answer

Sorry, but I think the answer is A

The question is asking for how many hours she has been charged.
That can only be 1 + 6 hours.

Even if she stayed 6,5 hours, she will still be charged for 7 hours.

The problem I think is that we looked for how long she parked, but we dont need that. We need the hours she has been charged.

I hope this will be correct.

Regards,

Alex

Alex_NL · Answer

I would also choose E

Statement 1 and statement 2 alone are insufficient.

Combined we get:

3,75 - 0,75 = 3,00
4,00 - 1,00 = 3,00

This still doesnt tell us how many additional hours she parked her car.

What is the OA and what is there explanation?

Regards, 

Alex

ywilfred · Answer

Hi Alex,

The OA given is A. Here's the reasoning the OG gave:

Statement (1) gives the charge for the first hour and for subsequent hours. From this information, together with the total charge that is given, the number of hours after the first hour can be computed.

Now I have misgivings about the explanation here. The question obviously stated this: "parking charges at the garage are 75 cents for the first hour and 50 cents for each additional hour or fraction of an hour".
What the explanation does is to ignore the last phrase "faction of an hour"

ywilfred · Answer

To elaborate a bit more:

$0.75 - hour 1
So $3.75-$0.75 = $3.00

If the question has stated only this : "$0.50 for subsequent hours", then we're pretty fine. All we need to do is to divide $3.00 by $0.50 to find out how many hours she has parked at the garage after the first hour.

However, the statement says it's $0.50 for each additional hour or fraction of an hour"

Now we can have a number of possibilites:

Parked 6 hours - $3.00
Parked 5.5 hours - $3.00
Parked 5.75 hours - $3.00
and so on... 
So we can't really tell how many more hours she actually parked her car at the garage.

It's scary that even OGs might make mistakes. If that happens on an actual GMAT, I think I'll be pretty mad.

ChallengeBound · Answer

Alex is right. ETS goes to great lengths to avoid ambiguity in questions. The stimulus states explicitly "for how many hours of parking was  she charged " A is the answer.

TheNightKing · Answer

Bunuel 
Hello Sir
(1) Parking charges at the garage are $0.75 for the first hour and $0.50  for each additional hour or fraction of an hour. 
I was confused by the words "fraction of an hour". Ideally this sentence can mean "for each additional hour" or for each fraction of an hour which can be 1/2,1,4 etc. What am I missing?

Bunuel · Answer

"Parking charges at the garage are $0.75 for the first hour and $0.50 for each additional hour or fraction of an hour" means that the parking time will be rounded up to the whole hour. For example: 
If Nan parked a car for 3/4 hours, she would be charged for 1 whole hour = $0.75
If Nan parked a car for 1 1/4 hours, she would be charged for 2 whole hours = $0.75 + $0.50.
If Nan parked a car for 10 8/9 hours, she would be charged for 11 whole hours = $0.75 + 10*$0.50.

TheNightKing · Answer

That makes sense!
Good Morning and Thank you!

Hovkial · Answer

OFFICIAL GMAT EXPLANATION

Statement (1) gives the charge for the first hour and for subsequent hours. From this information, together with the total charge that is given, the number of hours after the first hour can be computed. Thus, the answer must be A or D. From statement (2) the charge for the first hour can be determined; however, there is no information about charges after the first hour. Therefore, (2) alone is not sufficient, and the best answer is A.

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Yesterday, Nan parked her car at a certain parking garage

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Yesterday, Nan parked her car at a certain parking garage

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