Auditor: XYZ, a construction company, purchased

Auditor: XYZ, a construction company, purchased 20 new trucks 3 years ago, and there is no record of any of those trucks being sold last year. Records indicate, however, that XYZ sold off all of its diesel-powered trucks last year. We can thus conclude that none of the 20 trucks purchased 3 years ago were diesel powered.

No record of those trucks were sold last year —> none of them were diesel powered.
(Those sold last year = diesel)

Leap: Just because they were not sold last year does NOT indicate that non of them were not sold at any time before that. So it is possible that some of the new trucks which are diesel-powered were sold 2 years ago. This must not be true otherwise the conclusion will break down.


Which one of the following is an assumption required by the auditor's reasoning?

We know this. Why tell us again? (A) is out.
Does this imply those new trucks are not diesel-powered? (B) is out.
Trucks other than those 20 trucks 3 years ago are irrelevant.
So this eliminates the possibility that the 20 truck were sold 2 years ago. Hang on to this.
[quote]v(E) XYZ no longer owns any trucks that it purchased more than 3 years ago.[/quo
te]
You don't own any more trucks. So you sold them all. Perhaps you sold them 2 years ago because they were diesel-powered that you don't like anymore. This matches our thought that weakens the argument. (E) is out.

Only (D) is left. D is our correct answer.

Struggling with this one for some reason.
Please help.

Let us break the stimulus down into premises and conclusion:

Conclusion: None of the 20 trucks purchased 3 years ago were diesel powered.

Premises (reasons/facts supporting the conclusion):

i) XYZ purchased 20 new trucks 3 years ago.
ii) There is no record of any of those trucks being sold last year.
iii) XYZ sold off all of its diesel-powered trucks last year.

We can see a clear gap in the reasoning. All of XYZ's diesel powered trucks were sold off last year and there is no record of any of the 20 new trucks that were purchased 3 years ago being sold last year. However, the conclusion is about all the trucks not being diesel powered. Clearly, in order to draw this conclusion, we need to know if any of the 20 trucks were sold in the years preceding last year as well, and whether any diesel powered trucks were sold in that period.

Let us analyze the options:

(A) All of the trucks that XYZ sold last year were diesel powered. This does not tell us anything about the period before last year and hence does not help in the conclusion. Eliminate.

(B) XYZ did not purchase any used trucks 3 years ago. There is nothing about used trucks in the stimulus. Irrelevant. Eliminate.

(C) XYZ did not purchase any new trucks since it purchased the 20 trucks 3 years ago. This does not tell us anything about what happened to the trucks after purchase and hence does not help in the conclusion. Eliminate.

(D) None of the 20 trucks was sold before last year. Correct answer. If none of the 20 trucks was sold before last year, none was sold last year either and XYZ sold all of its diesel powered trucks last year, then none of the 20 trucks were diesel powered.

(E) XYZ no longer owns any trucks that it purchased more than 3 years ago. Same as (C). Eliminate.

Hope this helps.

akela / mysterymanrog
Typo in (E), it should be "more" not "n1ore"

____________________
Fixed that. Thank you!

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We could see this kind of reasoning in DI.

Premises:
XYZ purchased 20 new trucks 3 years ago, and there is no record of any of those trucks being sold last year.
(so say XYZ bought T1, T2, T3, ... T20 3 years ago but in last yr records none of them is being shown as sold)

Records indicate, however, that XYZ sold off all of its diesel-powered trucks last year.
(all diesel trucks it had, it sold off last year. Now either it has no diesel trucks or it bought new ones this year. Say T21 - T30 were the only diesel powered trucks XYZ had last year and all were sold off.)

Conclusion: None of the 20 trucks purchased 3 years ago were diesel powered.
(T1, T2, T3, ... T20 are not diesel powered)

The logic seems reasonable. If there has to be assumption here, it means there is a statement which when negated will prove the conclusion wrong. What could establish that say T1 was indeed diesel powered?
If T1 was diesel powered but was already sold off 2 years ago, then it all works out. Then T1 could be diesel powered, it would not have been sold last year and all diesel powered trucks could have been sold off last year. This is what option (D) says.

(D) None of the 20 trucks was sold before last year.
If we are to conclude that T1 to T20 were not diesel powered, then it must be true that none of them was sold off prior to last year. If none of them was sold off prior to last year and we know that none of them was sold off last year but last year all diesel trucks were sold, then it makes sense that T1 to T20 are all non diesel trucks.
Correct.

(A) All of the trucks that XYZ sold last year were diesel powered.

We know that all diesel trucks were sold. There is no assumption required that all trucks sold were diesel only. Perhaps all diesel trucks were sold and some petrol trucks were also sold. Nothing mentioned in the argument.

(B) XYZ did not purchase any used trucks 3 years ago.

The whole argument is only about those 20 new trucks bought 3 years ago. XYZ could have bought some used trucks also 3 years ago. No such assumption.

(C) XYZ did not purchase any new trucks since it purchased the 20 trucks 3 years ago.

No such restriction. It could have bought 100 trucks and kept or sold them.

(E) XYZ no longer owns any trucks that it purchased more than 3 years ago.

No such restriction. It could have bought a petrol truck 20 years ago and could still be holding it.

Answer (D)

Discussion on Assumption Questions: https://youtu.be/O0ROJfljRLU
A Hard Assumption Question: https://youtu.be/0j4tovGifIg