Q19 - XYZ Trucks

[smiller]

Question Type:
Necessary Assumption

Stimulus Breakdown:
Premises:
1. A company purchased 20 new trucks three years ago.
2. There is no record of any of those trucks being sold last year.
3. Records indicate that the company sold all of its diesel-powered trucks last year.

Conclusion:
None of the 20 trucks mentioned in the first premise were diesel-powered.

Answer Anticipation:
The auditor seems to think that, if any of the 20 trucks mentioned in the first premise were diesel-powered, they would have been sold last year along with all of the other diesel trucks. One problem with this reasoning is that some of those 20 trucks, or all of them, could have been sold two years ago. We only know about the trucks that were sold last year.

Correct Answer:
(D)

Answer Choice Analysis:
(A) This answer is irrelevant. We don't have to assume that all of the trucks sold last year were diesel-powered. If the 20 trucks that were bought three years ago were diesel-powered, and they were still around last year, they should have been included in the trucks that were sold. This would be the case even if the company sold a few electric-powered trucks, too (don't laugh, Elon Musk probably has them on the drawing board).

(B) This is also irrelevant. If the company did purchase some used trucks three years ago, or didn't, that wouldn't help us decide whether any the 20 new trucks were diesel.

(C) This is irrelevant for reasons similar to (B). Reports indicate that the company sold some trucks last year. Those trucks could have been purchased after the 20 new trucks, or before. It wouldn't affect the conclusion either way.

(D) This is the correct answer. If we're concluding that none of the 20 new trucks were diesel-powered because they weren't among the trucks sold last year, we have to assume that the company still owned those 20 new trucks last year. For this to be true, we have to assume that they weren't sold before last year.

(E) This is another irrelevant answer. We don't care if the company does or doesn't own any of the trucks that it purchased more than three years ago. Maybe, for sentimental reasons, the owner still owns the first truck he ever bought. This doesn't tell us anything about the 20 new trucks from three years ago.

Takeaway/Pattern: When premises describe events happening in a certain time period, look for holes in the timeline. What period of time, or possible events, are being ignored in the conclusion?

#officialexplanation

[T.J.]

Since no one has posted any question regarding this one, let me give my 2 cents.

It might look complicated on the surface. It certainly did in my experience of doing this test. After review, the concept turns out to be rather simple.

In a nutshell, the argument hinges on the fact that 20 new trucks purchased 3 years ago and all the diesel trucks sold off are mutually exclusive. The exclusivity is established if we supply the assumption that none of the 20 trucks was sold before last year. Note the gap exists between the time period of 3 years ago and last year.

If we have sold off all the diesel trucks but all the 20 trucks remain, we can be sure that these 20 trucks are not diesel powered since all the diesels are gone.

[pewals13]

Core:

XYZ bought 20 new trucks three years ago none of which were sold last year + XYZ sold off all of it's diesel powered trucks last year---------->None of the 20 trucks purchased 3 years ago were diesel powered

What absolutely needs to be true for conclusion to be reached?

Answers choices:

(A) There could have been one non-diesel truck that was sold last year, this doesn't impact whether the cohort we're interested in had any diesel trucks

(B) Used trucks are out of scope, you only care about diesel trucks and the 20 new trucks purchased three years ago

(C) Out of scope. You're only interested in the cohort of trucks purchased three years ago. If 1,000 new trucks were purchased it doesn't change the relationship between the premises and the conclusion

(D) If some of the 20 trucks were sold before last year, the fact that none of them were sold last year does not guarantee that none of them were diesel. There could have been a number of diesel trucks that were a part of the 20 that were sold before last year.

(E) Suppose XYZ owned one truck that was bought back in 1946. Does this impact the reasoning?

[renata.gomez]

I thought I would add what tripped me up. I misread "sold of last year". I thought it meant that all of the diesel trucks were sold in that single year preceding the current year. Now that I see it as it couldve taken an X amount of years to sell them. the point is that there's no more diesel trucks, not that they were all sold last yr.