#18 - Global, Cannot Be True

[Administrator]

Complete Question Explanation
(The complete setup for this game can be found here: lsat/viewtopic.php?t=4751)

The correct answer choice is (D)

This is a very difficult question, even with the templates. Here is how the four incorrect answers can be eliminated:

Answer choice (A) can be eliminated because Template #4 shows this is possible: R tests J on the second day, and S has the option of testing J on the first day.

Answer choice (B) can be eliminated because Template #3 shows this is possible.

Answer choice (C) can be eliminated because Template #4 shows this is possible: Y tests G on the second day, and R has the option of testing G on the first day.

Answer choice (E) can be eliminated because Template #4 shows this is possible: Y tests F on the second day, and T has the option of testing F on the first day.

The problem is that, at first glance, the remaining answer, answer choice (D), also appears possible, via Template #1. But, this is the one answer to feature the variable in question—G—in two double-options (all of the other answers feature no double-options or just one double-option). When you have two double-options, there may be other relationships at work that thwart the natural possibilities of each option. That is what occurs here:

In answer choice (D), only Template #1 could provide an answer where both S and T test G. But, when S tests G the first day, R then tests J on the first day, which means that R cannot test J on the second day. The only spot left is then T, which means that S and T cannot both test G when S tests G on the first day. A similar sequence occurs when T tests G on the second day. Thus, S and T cannot both test G, and answer choice (D) cannot be true and is correct.

[jared.xu]

This third logic game is a hybrid of linear and grouping games. Am I correct in using day 1 and 2 as the base because of the inherent sense of order, and in having J, H, G, F stacked one on top of the other on the left side of the diagram to create 4 rows? I have a "not law' for R on F's row, and a "not law" for Y on J's row. I also show that 1 T will be placed in H's row.

Both questions 16 and 18 seem to consume a lot of time. It took me 6 min 45 sec just to get through those two questions alone. Obviously, I won't have that luxury on test day. Could you please tell me whether there are any other ways to attack these two "cannot be true" questions besides drawing out a diagram to try out each answer choice? I could not see any inferences that could be helpful. Thank you in advance for replying.

[Nikki Siclunov]

Hey,

Thanks for your question. Why not create four templates based on the following two rules:

(1) the bike that Y tests on the first day must be tested by S on the second day, i.e. you have a YS block that can only fit into two of the four groups (Yuki cannot test J, and Teresa must be a tester for H, so the YS block cannot be assigned to H either);

(2) T must be assigned to H either on Day 1 or Day 2

Each of these rules gives you two options, so 2x2 gives you 4 templates to work with. It takes 3-4 minutes to set them up, but then you can breeze through the questions in no time. Try this out.

[jared.xu]

Thank you so much for your suggestions. I did this logic game section again, and used the four templates you suggested in this game. But I still find that to answer Q16 and 18, I have to try out each answer choices one by one. The templates you suggested definitely made it easier. But I only see two routes that I could take: either redraw the diagrams (the appropriate templates) for each answer choices and plug in the answers to see whether they work or not, or plug each answer choices into the actual templates (into as many of the four as possible) and then erase them once I find that they work so that I could plug in the next answer choice. Which of the two options do you think is better. I know that the Logic Games Bible does not recommend deleting the works we've done already. But are Q16 and 18 exceptions to the rule? It would definitely be faster to erase a few letters from the four templates than to redraw entire templates for each answer choices.

Or are there still hidden inferences to this game that I have not discovered yet? Thank you in advance for replying.

[Nikki Siclunov]

Question 16 should be made immediately apparent by the four templates, without the need of additional local diagrams. I suspect you did not fully examine the placement of variables within each template. According to all four templates, the second rider for F is either S or Y (therefore, it cannot be Teresa). Here's why:

Whenever the YS block tests F (Y on the first day, S on the second), the second rider for F is obviously S. However, when the YS block tests G, the second rider for F is always Y. Do you see why? Try both options for T (T must test H either on day 1 or day 2) and analyze the placement of the other variables. You will see that Y is always testing F on the second day.

The same is true for question 18. If you filled out your four templates completely, you'd realize that four of the answer choices state proven possibilities of placing a pair of riders with each bike. There is no template, however, in which both S and T test G. If S tests G on the second day, Y tests G on the first. Alternatively, if S tests G on the first day, the only riders that can be on the second day are Y or R.

[jared.xu]

Thank you so much for that explanation. I now understand my problem. When you first told me about the four templates, I didn’t know that it would be possible to fill them out completely, I just thought that there were too many possibilities. And the reason that I did not spend time looking through the possibilities is because of a lesson I learned while trying to solve Game #3 of Dec 2001. Powerscore’s LSAT Logic Games Ultimate Setups Guide discusses this game (Game #3 of Dec 2001) thus: “only seven templates containing fourteen possibilities exist in this game. Although one approach could be to identify each of these templates, there are likely too many templates to be able to show each within the time limits of the game. Normally, we would prefer to draw out four or five templates at most. With the variety of rules, you should remember that using hypotheticals can be a very effective weapon (122). Before checking out the Ultimate Setups Guide’s explanations, I did the game and tried to come up with templates starting with the GH block and to fill them out. It indeed ended up taking too much time, and I abandoned the template idea midway through because I couldn't be sure I had identified all of them. And even after abandoning this approach, I ran out of time because I already spent too much on trying fill out the templates. But it would appear that on this Bicycle Game of Oct 2011, I overcorrected myself. Even when you told me about the four templates, I just drew them out without trying to fill them up. And then I mistakenly viewed each answer choices of Q16 and 18 as hypotheticals to be plugged into the four templates. Would you say that if there are four or five templates, we should always do our utmost to fill them all up before going to the questions? It certainly seems to work out that way in this game, but would you say that this is a good general rule? Thank you again for your help.

[Nikki Siclunov]

Absolutely. When you undertake a template approach, you should strive to complete each template as fully as possible, making as many inferences as the rules allow. Granted, chances are you won't be able to determine the placement of every single variable, so at times it will be necessary to set up dual or split options. Most of the time, it is unnecessary to break these down into separate possibilities. But the greatest benefit of setting up templates it the ability to see how the game is solved for each option you examined. Think of it as a highway in which you have, let's say, 4 exits: you want to go down each exit as far as possible, without getting lost in some of the side streets that branch off of them

Hope that makes sense.