#16 - Global, Could Be True

[Administrator]

Complete Question Explanation
(The complete setup for this game can be found here: lsat/viewtopic.php?t=11371)

The correct answer choice is (C)

Answer choice (C) is the correct answer choice because U and X could both repair R and T, or R and V. In each of the other four answer choices the pairs can never repair the exact same types (or numbers) of machines:

Answer choice (A) is incorrect because S repairs one machine and Y must repair two machines.

Answer choice (B) is incorrect because although U and Y can repair the same number of machines, U repairs R whereas Y does not.

Answer choice (D) is incorrect because although W and X can repair the same number of machines, X repairs R whereas W does not.

[jared.xu]

I got this question right. But I have a question about the phrase "all and only" in the question. The way I understand "all and only" in general is that it refers to a specific group. If one say, "I want all and only those who are 19 in group A," the use of this phrase is very clear. It means that the person wants everyone who is 19 and does not want anyone who is not 19 in the group A. However, given the context of question 16, I am certain about the function of the phrase. If you say, "which one of the following pairs of technicians could repair only the same types of machines as each other," would you not be saying the exact same thing? If you take out only and use "all," ("Which one of the following pairs of technicians could repair all the same types of machines as each other," the sentence no longer seems to make any sense. Does it mean both technicians repairs all the machines? Or does it mean the same as "only," i.e., both technicians repair only the same types of machines as each other?

From the context, one could guess "all and only" mean "exactly" in this question. But I would like to know what function "all" plays here, and why the test makers would choose to use the phrase "all and only" in this question. Thank you in advance for replying.

[Jon Denning]

Hey Jared - thanks for the question. I think you can look at a phrase like "all and only those" here as a very precise group: everyone with a characteristic, and no one without it. This is a bit like a "complete and accurate" list type question in games ("which of the following is a complete and accurate list of people who could perform third?") where the answer choice includes everyone of a certain type, and no one not of that type. So it sets both a minimum (all) and a maximum (only).

Does that make sense?

[jared.xu]

Hey Jon, Thank you for the explanation. You just confirmed my suspicions that the use of "all" is useless in this context, a simple "only" would do. The question asks: "Which one of the following pairs of technicians could repair all and only the same types of machines as each other." It is pretty clear that repairing "the same types of machines as each other" does not need both a minimum (all) and a maximum (only). It merely needs a maximum (only), What do you think would be the minimum (all) for repairing "the same types of machines as each other"? Is it right to say that "which one of the following pairs of technicians could repair all and only the same types of machines as each other" means the exact same thing as " "which one of the following pairs of technicians could repair only the same types of machines as each other? Thank you in advance for replying.

[Jon Denning]

Yeah I think in that specific case "only" would be enough to know that it had to be an exact match.

[hope]

E seems to fit the bill also. Since X can have all three: VTR then X is exactly like Y: VTR. What saith anyone? Thanks.

[Robert Carroll]

Hope,

Y cannot have all 3, though. In fact, Y is always restricted to T and V. Because Y has T and V via the second rule, yet cannot have anything in common with S, via the third rule, Y has T, V, and never R. S must have R to repair something, fulfilling the requirement in the scenario that "Each technician repairs machines of at least one of the following three types". X must of course repair R via the first rule, so X and Y will always differ at least on radios - one must repair them, the other cannot. See the setup thread for more on all those inferences: https://forum.powerscore.com/lsat/viewtopic.php?t=11371

Robert Carroll