#12 - Local, Not Necessarily True, Suspension, False to True

[Dave Killoran]

Complete Question Explanation
(The complete setup for this game can be found here: lsat/viewtopic.php?t=885)

The correct answer choice is (E)

The question stem suspends the final rule of the game, and instead specifies that exactly one light on the north side is on. From the fifth rule, then, the north-side light that is on must be light 2, and lights 1 and 3 are off:

PT8-Jun1993 LG Explanations game 2 #12 diagram 1.png

At this point, answer choices (A), (B), and (C) can be eliminated as each must be true.

From our discussion of the fifth rule, when any corner light is off, then the center light on that side must automatically be on. Thus, because light 3 is off, light 4 must be on:

PT8-Jun1993 LG Explanations game 2 #12 diagram 2.png

Because light 4 is on, answer choice (D) can be eliminated. Consequently, only answer choice (E) remains, and (E) is the correct answer.

[allik@umich.edu]

Hello,

I had the setup correct and understood the game, yet had trouble with #12. Could someone please explain #12 to me?

Thank you!

[Nikki Siclunov]

Hi allik,

Thanks for the question, and welcome to the forum!! Assuming you understand the setup and the inferences, I'll dig right in.

This Local, Rule Suspension question asks you to suspend the condition requiring two of the lights on the North side to be (+). Instead, exactly one light on that side must be (+). According to the fifth rule, that light must be the center light, and so light 2 must be (+). Lights 1 and 3 must be (-). Clearly, answer choices (A), (B), and (C) must all be true.

What about the East side? We know that light 3 must be (-). If two lights on that side are (+), those lights will be 4 and 5. If only one light were (+), that light would need to be the center light (4). In either case, light 4 must be (+). This eliminates answer choice (D).

Answer choice (E) does not have to be true, and is therefore the correct answer choice to this Could Be False question.

Hope this helps!

[allik@umich.edu]

Thank you for this explanation! I understand your explanation, but am confused about why suspending that rule means that two of them still can't be on? Just because they don't have to be on, can't 1 and 3 still both be on?

[Dave Killoran]

Hi Allik,

The reason that can't occur is because of the wording in the question stem: "Suppose that it is no longer part of the specifications that two lights on the north side be on. If all of the other original specifications remain the same, and if exactly one light on the north side is on, which one of the following statements could be false?"

So, the question stem is what is specifying that exactly one light on the north is on, and that precludes 1 and 3 from being on at the same time.

Please let me know if that helps. Thanks!