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Complete Question Explanation

Assumption-SN. The correct answer choice is (D)

The premises in the stimulus establish the following logical relationship: "If there are holidays or vacation, John works less than five days in a week. If neither holidays nor vacation are present, John works five days per week." We are told that last week there were neither holidays nor vacation. The obvious conclusion is that John worked five days last week. We know that Friday he worked as a blacksmith. But how can we be sure that his other days of work were Monday through Thursday? Why are we so quick to dismiss the possibility that he worked on Saturday or Sunday? This is the missing assumption.

Answer choice (A): Apply the Assumption Negation test. Even if John sometimes takes a vacation of more than one week in length, it doesn't matter for the argument: we know that John had no vacation last week, so any consideration of vacation is irrelevant.

Answer choice (B): The argument is not really concerned with the amount of time that John worked on individual days. The argument is only making a claim about the identity of the individual days when John indeed worked.

Answer choice (C): Like choice (A), this statement is irrelevant. We know that neither vacation nor holiday occurred last week, so we have no reason to care about vacation or holiday.

Answer choice (D): This is the correct answer choice. Without the statement in this answer choice, it becomes very possible that John worked on days besides Monday through Thursday.

Answer choice (E): Apply the Assumption Negation test: What if there were some (at least one) days last week in which John worked both jobs? Would this destroy the author's argument? No: it is conceivable that John could have worked his insurance job on Monday, Tuesday, Wednesday, Thursday; and that John worked the blacksmith job on Thursday and Friday. This story is perfectly consistent with the premises of the stimulus.
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I guessed on this question, I really didn't understand this question at all and it, in fact, reminded me almost of a logic game question. is it possible to have the stimulus broken down into pieces I am just not understanding what it is telling me and what type of assumption I am looking for in this question.
 Adam Tyson
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Sure thing, egarcia! This stimulus is conditional, as indicated by the necessary condition indicator "except". When that is present, it indicates a necessary condition (to the right of your conditional arrow) and the other condition in the stimulus is NOT the sufficient condition. Rather, the NEGATION of that other thing is sufficient. We call that extra step the Unless Equation TM. So the diagram of the first sentence is this:

John works 5 days :arrow: Vacation OR National Holiday

(If John does not work 5 days then he is on vacation that week or else there is a national holiday, or maybe both)

The contrapositive is:


AND :longline: :arrow: John works 5 days

National Holiday

(If there is no vacation and there is no national holiday, then John has to work 5 days that week)

The stimulus then tells us that the original necessary conditions did not occur - there's no holiday and he's not on vacation. In other words, we have met the sufficient condition for the contrapositive, and can therefore prove that John worked 5 days that week.

Now the question is, WHICH 5 days? We know John works as a blacksmith on Fridays, and in the insurance company 4 other days. The author concluded that he worked there Monday through Thursday, but how would he know that? Who says it has to be THOSE 4 days? Couldn't he work Saturday, or Sunday, or both?

The assumption here is a defender assumption, one that fights off an attack. If we are saying "but wait, he could work the weekend, so maybe it isn't Monday through Thursday", the author must have assumed that it was NOT the weekend, fending off that objection. That gets you answer D, the correct answer here.

To prove it, try the Negation Technique TM on that answer - what if John DID work Saturday or Sunday or both? Then the claim that he worked Monday through Thursday would be completely false, since he worked 5 days including Friday.

With that big, juicy conditional claim just ripe for the picking in the first sentence, go ahead and diagram it. That way, with a little practice, arguments like these will become much clearer, and picking right answers will be about as easy as playing connect-the-dots.

Keep at it!
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Where does it state/imply that John cannot work in the insurance company on the same day that he’s working as a blacksmith? I read an earlier post that said he works as a blacksmith on Friday and has to work 4 other days in the insurance company but I don’t understand how that is established.

Why can’t John work Monday, Tuesday, and Wednesday exclusively in the insurance company and on Friday work in the insurance company as well as work as a blacksmith?
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Hi Amitjohn!

We don't actually know that John cannot work in the insurance company on the same day that he's working as a blacksmith. If you look at the description for answer choice (E) in the full explanation above, it states that it is perfectly fine for John to work some days at both the insurance company and as a blacksmith. He could work at both on Friday; he could work as a blacksmith on other days besides just Friday. But we do know from the first sentence that John works 5 days a week, so he cannot work Monday/Tuesday/Wednesday at the insurance company and Friday as a blacksmith and at the insurance company and that's it because that would only be four days a week, rather than five.

It might help to remember that the author's conclusion here does not necessarily follow from the premises we've been given. The majority of arguments on the LSAT are actually flawed, meaning that the premises as stated do not necessarily prove the conclusion as stated. That is especially true in Assumption questions, in which the author has assumed something to be true in drawing their conclusion but has not explicitly stated their assumption. All LSAT authors believe their conclusions to be true. So with Assumption questions, you have to ask yourself, if the author believes this conclusion is true, what else does the author have to believe?

In this case, the author believes that John worked at the insurance company on Monday, Tuesday, Wednesday, and Thursday last week. But, as you point out, his premises as stated do not fully prove that conclusion. So we're being asked to determine what the author must be assuming if he believes his conclusion to be true. Since we know that John always works as a blacksmith on Fridays, and the author thinks John must have worked at the insurance company on Monday, Tuesday, Wednesday, and Thursday last week, this means that the author must be assuming that John did not work on Saturday or Sunday, because his 5 days would be take up by the M/Tu/W/Th/F schedule the author says he must have worked.

Hope this helps!

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Thank you for the reply Ms. Woods! It was very thorough and helped me truly grasp the question as well as strengthened by approach to assumption questions in general.

It was pointing out that the stimulus states "John works five days each week..." that really helped clear things up. I now see that if John worked in the insurance company as well as a blacksmith on Friday, he would only be working four days out of the week.

Thank you again!

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