HOT Competition 31 Aug/8PM: It is impossible to determine how far Noor

Question

It is impossible to determine how far Noor has driven her car based solely on how many times she has had its oil changed, because she has not recorded how far she has driven her car since its last oil change. However, if she had not driven her car since its last oil change, one could calculate how far she has driven her car based solely on counting the number of oil changes and consulting her car’s manual, since Noor gets her car’s oil changed precisely as often as prescribed by the manual.

Which one of the following must be assumed in order for the argument’s conclusion to properly drawn?

A. The manual for Noor’s car prescribes getting the car’s oil changed once every 5,000 miles driven.

B. The manuals for different makes and models of car do not prescribe different distances between oil changes.

C. The manual for Noor’s car does not prescribe changing the oil more often after the car has been driven 100,000 miles than it does during the first 100,000 miles.

D. There is no way to figure out how far Noor has driven her car since its last oil change.

E. The manual for Noor’s car prescribes changing the car’s oil as frequently in warm weather as in cold weather.

Bunuel · Accepted Answer

Veritas Prpe Explanation

The correct answer is E.

This is a necessary assumption question. The correct answer must be something that the argument cannot live without – a statement that, if it were false, would destroy the argument.

In this case, the conclusion is that “if she had not driven her car since its last oil change, one could calculate how far she has driven her car based solely on counting the number of oil changes and consulting her car’s manual.” But why? Presumably, because the manual calls for oil changes at regular distance intervals. However, the argument never actually establishes this information. We need to address it in an answer choice.

Answer E may seem irrelevant at first. However, the Assumption Negation Technique offers key insight. If E were not true – if “the manual for Noor’s car does not prescribe changing the car’s oil as frequently in warm weather as in cold weather” – then one would have to know the weather conditions in which Noor had driven her car in order to know the significance of the number of oil changes. Has Noor’s car had many oil changes? Maybe the car has been driven a long distance, or maybe it has been driven a shorter distance but in cold weather. Using only the manual and the number of oil changes, without other information about temperature, it would be quite impossible to determine the distance driven. So the absence of E destroys the conclusion. E is necessary, and therefore E is correct.

Answer A is tempting; if the manual prescribes an oil change every 5,000 miles, then one could definitely calculate Noor’s miles driven. But while A is sufficient, it is not necessary. Even if the manual didn’t prescribe an oil change every 5,000 miles, it might prescribe an oil change every 10,000 miles, or every 3,000 miles, or at some other regular distance interval. And in each of those cases it would be no less possible to count the oil changes and calculate the distance traveled. Because A is not necessary, it is incorrect.

Answer B is simply irrelevant. Whatever the manuals for other makes and models of cars may say, Noor’s car’s manual is the only one that matters – the argument explicitly describes consulting “her car’s manual.”

Answer C is another extremely tricky wrong answer. Certainly, if the manual prescribes a different interval between oil changes after 100,000 miles, it is more work to calculate the distance based on the number of oil changes. But why should it not still be possible, with a bit of math? If the manual prescribes, say, one oil change every 10,000 miles until 100,000 miles, and then one oil change every 5,000 miles thereafter, then a car with, for instance, 13 oil changes would have been driven 10(10)+3(5)=115,000 miles. Since it is still quite possible that one could calculate how far Noor has driven her car, C is not correct.

Answer D, though superficially appealing, is another irrelevant answer. The argument’s conclusion is conditional, specifically premised on “if she had not driven her car since its last oil change.” Any answer choice that attempts to address this issue is therefore pointless. Furthermore, even if there were a way to find out how far Noor had driven her car since her its last oil change, this would in no way render it impossible to calculate the distance she has driven her car – in fact, it would seemingly make it easier. So D is also a bit of a backwards wrong answer.

piyush0122 · Answer

It is impossible to determine how far Noor has driven her car based solely on how many times she has had its oil changed, because she has not recorded how far she has driven her car since its last oil change. However, if she had not driven her car since its last oil change, one could calculate how far she has driven her car based solely on counting the number of oil changes and consulting her car’s manual, since Noor gets her car’s oil changed precisely as often as prescribed by the manual.

Which one of the following must be assumed in order for the argument’s conclusion to properly drawn?

A. The manual for Noor’s car prescribes getting the car’s oil changed once every 5,000 miles driven.- Incorrect. We already know that oil is changed according as often prescribed by the car manual. we do not care about the distance at which the oil is changed.

B. The manuals for different makes and models of car do not prescribe different distances between oil changes.- Incorrect. Out of scope. we are not bothered about the different models.

C. The manual for Noor’s car does not prescribe changing the oil more often after the car has been driven 100,000 miles than it does during the first 100,000 miles.- Incorrect. Even if the change in oil is prescribed more often after every 100,000 miles we can still calculate the distance travelled by the car as we can know the distance at which the oil change has been prescribed.

D. There is no way to figure out how far Noor has driven her car since its last oil change.- Incorrect. This is not an assumption.

E. The manual for Noor’s car prescribes changing the car’s oil as frequently in warm weather as in cold weather. - Correct. If oil changed is prescribed according to seasonal variations then we can obtain no information about the distance travelled by Noor's car. Negating this choice weakens the argument. Hence, It is the correct choice.

Kinshook · Answer

It is impossible to determine how far Noor has driven her car based solely on how many times she has had its oil changed, because she has not recorded how far she has driven her car since its last oil change. However, if she had not driven her car since its last oil change, one could calculate how far she has driven her car based solely on counting the number of oil changes and consulting her car’s manual, since Noor gets her car’s oil changed precisely as often as prescribed by the manual.

Which one of the following must be assumed in order for the argument’s conclusion to properly drawn?

A. The manual for Noor’s car prescribes getting the car’s oil changed once every 5,000 miles driven.
This is a valid assumption based on which conclusion may be drawn but it is not required that the assumption must be assumed in order for the argument's to be properly drawn.
Incorrect

B. The manuals for different makes and models of car do not prescribe different distances between oil changes.
Noor knows make and model of her car and has manual for the same make & model.
Incorrect

C. The manual for Noor’s car does not prescribe changing the oil more often after the car has been driven 100,000 miles than it does during the first 100,000 miles.
Even if the manual prescribes changing oil at different mileage based on kilometers driven by car, still number of kilometers driven by the car can be found.
Incorrect

D. There is no way to figure out how far Noor has driven her car since its last oil change.
There are multiple ways to find out kilometers driven by the car. 
Incorrect

E. The manual for Noor’s car prescribes changing the car’s oil as frequently in warm weather as in cold weather.
This assumption must be true since if car is driven in one type of weather requires different frequency of oil change than in other type of weather, then number of kilometers driven by the car can not be calculated. 
Correct

IMO E

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HowdyPartner · Answer

Howdy -- explanation and reference below.

------------
It is impossible to determine how far Noor has driven her car based solely on how many times she has had its oil changed, because she has not recorded how far she has driven her car since its last oil change. However, if she had not driven her car since its last oil change, one could calculate how far she has driven her car based solely on counting the number of oil changes and consulting her car’s manual, since Noor gets her car’s oil changed precisely as often as prescribed by the manual.

Which one of the following must be assumed in order for the argument’s conclusion to properly drawn?  assumption question -- what must be true to go from premises to conclusion? Make sure to deconstruct argument.

Argument has 1 main conclusion -- that is that they could find the number of miles driven if she did not drive since last oil change.

A. The manual for Noor’s car prescribes getting the car’s oil changed once every 5,000 miles driven.  Out of scope and way too specific here. We don't need an actual value and this value is not required.  Eliminate.

B. The manuals for different makes and models of car do not prescribe different distances between oil changes.   This argument says "her car’s manual" -- so we can assume that it is for her make and model.  Eliminate.

C. The manual for Noor’s car does not prescribe changing the oil more often after the car has been driven 100,000 miles than it does during the first 100,000 miles.  Does not matter -- as long as still able to calculate.  Eliminate.

D. There is no way to figure out how far Noor has driven her car since its last oil change.  This does not go with conclusion. This goes with first part of passage, and is not relevant here. Talking about whether they could figure it out based only off only changes.  Eliminate.

E. The manual for Noor’s car prescribes changing the car’s oil as frequently in warm weather as in cold weather.  Now this is a great answer. This is an outside factor that could affect the oil change, yet seems like out of scope. However, must be assumed here so this is our answer.   Our Answer.

--

Saupayan · Answer

This isn't necessary. (It is sufficient, but we don't care about sufficient in assumption). What if it said every 6000 miles? That would be fine too. So, negation test fails.

Irrelevant: We aren't concerned with other cars. We are concerned with Noor's car and the manual of that specific car. How does it matter if other cars specify same or different distances.

This may look tempting, but not really. Even if it specifies, say oil change every 1000 miles for 100k miles, and every 2000 miles after 100k miles, then too we would be able to calculate total distance just from those facts. So, the oil change may or may not be recommended more often, but we can still calculate all the same

1. This is no necessarily true. We can check the odometer for example. Or maybe just ask her. Whatever.
2. This isn't relevant to the conclusion. How is this a REQUIRED condition for us to be able to determine number of miles from number of oil changes?

This is the right answer. Because if it does specify different distances in different kinds of weather, what that means is we would also need to know how many oil changes were done in which type of weather. Because 5 oil changes in warm weather mean 5000 miles, whereas 5 oil changes in cold weather may mean 1000 miles (or some other numbers) unless they are the same in both types of weather. Since we want to determine the number of miles based just on the number of oil changes, this is a necessary condition

Answer: E

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JonShukhrat · Answer

The argument: it is impossible to determine the mileage relying solely on the number of oil changes.

Hypothetical situation: if she hadn’t driven her car since the last oil change, then...

Conclusion: then we can determine the mileage by counting the number oil changes and consulting her car’s manual.

So, the author assumes that there are two factors that would suffice:
1. Number of oil changes. 
2. Information given in the manual that tells how frequently the oil needs to be changed.

Keeping these in mind, let’s analyze answer choices:

A. The manual for Noor’s car prescribes getting the car’s oil changed once every 5,000 miles driven.

Negation: oil needs to be changes not every 5000 miles. Does the conclusion fall apart? No. It can be 4000 or any thousand miles. If knew that the oils was changed once every 4000 miles, then multiplying this number with number of changes we can still determine the mileage.

B. The manuals for different makes and models of car do not prescribe different distances between oil changes.

This choice overlooks “her car’s manual” part of the argument. The author is going to consult her car’s manual, not any other car, and thus this choice has nothing to do with the argument.

C. The manual for Noor’s car does not prescribe changing the oil more often after the car has been driven 100,000 miles than it does during the first 100,000 miles.

An alluring trap. 
Negation: let’s assume that the manual mentions two different frequencies before and after 100,000 miles. When below, change once every 5000, and when above change once every 3000. Let the number of oil changes be 30. We know that the first 20 change make up 100,000 miles and the remaining 10 constitutes 30,000 miles. So, C isn’t an assumption.

D. There is no way to figure out how far Noor has driven her car since its last oil change.

The argument has already mentioned that Noor didn’t record her mileage after changes oil last. This information is given as a truth that shouldn’t be challenged and hence we accept it with no doubt.

E. The manual for Noor’s car prescribes changing the car’s oil as frequently in warm weather as in cold weather.

Bingo, the correct choice.
Negation: oil change frequency is different during cold and warm seasons. Let’s assume that car needs oil change once every 5000 miles i warm weather and 4000 miles in cold weather. We don't know when the car was bought and how many cold and warm seasons it underwent. To find out this we will have to ask Noor about when she bought her car. However, in this case Noor will become the third source of information, contradicting the conclusion that two sources will be enough.

Hence  E

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Mizar18 · Answer

Premises

-Impossible to determine how far has driven, since she has not recorded how far driven since its last oil change.

-Change oil precisely as often as prescribed by the manual

Conclusion

But if the had not driven her car since its last change, one could calculate how far solely counting oil changes + consulting manual

A. The manual for Noor’s car prescribes getting the car’s oil changed once every 5,000 miles driven.

We do not need this one to the argument to hold. This one just gives more information about what is supposed to be said at the manual.

B. The manuals for different makes and models of car do not prescribe different distances between oil changes.

Do we need that manuals for different makes and models be the same? Not really, we just need that the accurate information for the relevant model is correctly stated at the manual.

C. The manual for Noor’s car does not prescribe changing the oil more often after the car has been driven 100,000 miles than it does during the first 100,000 miles.

Seems good… given that the calculation is based on # of change oils, you have to assume that there is no consideration regarding changing the oil more often in any of the kilometer thresholds 
Hold on this one.

D. There is no way to figure out how far Noor has driven her car since its last oil change.

This is stated at the passage. In addition, the point of the argument is that we can do the approximate calculation based on the number of change oils

E. The manual for Noor’s car prescribes changing the car’s oil as frequently in warm weather as in cold weather.

This one explains a particularity of the change oil, not relevant to the point of calculation based on the number of change oils.

C) is the answer.

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MayankSingh · Answer

IMO E

Argument : 
(i) Since Noor has not recorded how far she drove after last oil change, it is not possible to determine how far Noor has driven her car based solely on how many times she has had its oil changed
(ii) Considering distance traveled after last oil change to be zero, how far she has driven her car based solely on counting the number of oil changes and consulting her car’s manual, 
(Note: Noor gets her car’s oil changed precisely as often as prescribed by the manual).

Conclusion:   Distance traveled by Car can be calculated solely by counting the oil change & consulting Car's manual.
  Pre-thinking  : There is a correlation between distance traveled & oil change, and the oil change frequency is not affected by any other factors other than distance traveled.

Which one of the following must be assumed in order for the argument’s conclusion to properly drawn?

A.  The manual for Noor’s car prescribes getting the car’s oil changed once every 5,000 miles driven.  -   Incorrect   -
 This option need not be true for the conclusion to stand true. Negating this option becomes- Noor car manual not prescribe oil change once every 5000 miles- this is ok, may be the car manual would be prescribing some other number. but the conclusion would still true. So, negation doesn't break the conclusion. This option is wrong.

B.  The manuals for different makes and models of car do not prescribe different distances between oil changes.    Incorrect   -
 This option is irrelevant. We are only concerned with only change interval & distance traveled by Noor Car. other car & manual is not in scope & nothing need to be assumed in that direction.
 
C.  The manual for Noor’s car does not prescribe changing the oil more often after the car has been driven 100,000 miles than it does during the first 100,000 miles.    Incorrect   -
 Ok lets analyse this.  Lets negate this option - Manual for Noor's Car prescribe more oil change after 10,000 miles than during the 100,000 miles.
eg: first 10,000 Km - prescribe 5 times oil change at an interval of 1K, 2K,3k, 5K km & for next 1000 km prescribe 10 times at interval of 1K each. But from this data also we can calculate the distance traveled solely by knowing the no. of oil change. This doesn't break the conclusion. So this option is incorrect.

D.  There is no way to figure out how far Noor has driven her car since its last oil change.    Incorrect   -
 As stated in the argument itself, there is a way to record , but since Noor has not done that since her last oil change, it is impossible to determine the distance driven by the car. Assumptions are unstated premise that is necessary for the conclusion to hold true, So, the above not be assumed for conclusion to stand.

E.  The manual for Noor’s car prescribes changing the car’s oil as frequently in warm weather as in cold weather.    Correct  
  Lets negate this option:    The manual for Noor’s car not prescribes changing the car’s oil as frequently in warm weather as in cold weather. i.e say manual prescribe more in summer and less in winter. Let say- In Summer 5# times whereas in Winter 7# times for the same kilometer., but if a person is told that a "n" number of oil change has taken place, he may not be calculate the distance solely by knowing the oil change, weather condition is must to be know. Negation breaks the conclusion, so correct answer .

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saby1410 · Answer

GMATGuruNY   IanStewart

what is the conclusion of above argument?

VerbalBot · Answer

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HOT Competition 31 Aug/8PM: It is impossible to determine how far Noor

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