This is an explanation of the third logic game from Section III of LSAT Preptest 76, the October 2015 LSAT.
There will be a special art exhibit at a campus which will run from Monday through Friday (M, T, W, T, F). Each day is divided into two shifts and with five students working two shifts each. The students are Grecia, Hakeem, Joe, Katya, and Louise (G, H, J, K, L). You must determine who works the shifts based on the rules.
Game Setup
Time on second attempt: 3:52
See “repeating games” at bottom of section
Note: I did well the first time I did this game, but then I botched my first repeat. I tried to do upfront deductions, and it really, really didn’t work. I tried again about a week afterwards, using the method in the explanation below, and got the very fast time above. I believe the method below is far superior and faster than using upfront scenarios.
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People sometimes ask me how much work to do upfront on logic games. It used to be the case that you could deduce a lot before you even started.
But on new games, I find I rarely deduce anything. I tried to deduce stuff on my 2nd run through this game, and botched it. I did far better, and faster, on my first run through when I just listed the rules.
So unless deductions are really obvious, you probably shouldn’t be making any or many on new LSAT logic games. Instead, you want to focus on three things:
- Making a clear diagram
- Making a clear list of rules
- When possible, putting rules directly on the diagram instead of into a list
Here’s how I set up my main diagram:
(Note that on my actual page, I left off the MTWTF. It’s cleaner and faster to avoid them. But I draw them on these explanations for clarity.)
I already drew a few rules on the diagram: No L in shift 1, no G in shift 2, and K must be on Tuesday and Friday.
Here’s the other rules:
A couple notes:
The XX is shorthand for the same person can’t go twice on the same day.
G + G means that there’s at least one space between the two G’s.
1+ beside H/J means there’s at least one place where they’re together.
On older games, I used to have to explain the setup and make deductions. But increasingly I find there’s little to do except list the rules and memorize them.
You should be memorizing the rules. If you forget them, you’ll go slow and make mistakes. Not forgetting rules is the single biggest factor that allows people to score perfect on logic games.
Note for efficiency: On my own page, I drew a line between the rules numbered 2 and 3, and put an x through it. This was to remind me that L and G couldn’t go together. Then I didn’t draw the rule numbered 5.
This is somewhat more efficient, but I thought it would be less clear for the explanation, so I went with the version I drew above.
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Repeating Games
I’ve written elsewhere about the benefits of repeating games, to solidify your intuition for deductions. Note that the purpose of repeating games is to prove the answers right, so it doesn’t matter if you remember the right answer.
I repeated this game about three days after I first saw it, by which time I had forgotten the answers. I’ve written how long it took me on the second attempt. That time, or a couple minutes above it, is roughly the standard you should be aspiring to – a lot of people take 8-9 minutes on a repeat attempt, get everything right, and pat themselves on the back. But that’s too slow. The faster you go when repeating, the faster you’ll learn to go the first time you see a game.
(I say “a couple minutes above” my time because, after years of teaching the LSAT, I’m really, really fast. You should be almost as fast as me, but you don’t exactly need to match my pace to score -0.)
Time on second attempt: 3:52
Note: I botched my repeat. I tried to do upfront deductions, and it really, really didn’t work. So I’m not sure how long I’d repeat. However, my initial attempt was 9 minutes or less, I think.
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Nathaniel says
Hi, I know that the upfront deductions may not have worked for you on your second round through, but I would say that they are actually more useful on this game than any other I’ve run into so far. This was a tough game that I ended up wasting a lot of time on when running the full section timed, and I think applying my method below to other games could be very helpful, as it resulted in what are the only three possible diagrams (when making H/J interchangeable) for the entire game.
Step 1. We know that we have to have an H/J pairing, and that it can’t be Tuesday or Friday since we already have a K in those, leaving 1, 3, and 4.
Step 2. Notice that if you put the H/J pairing into Wednesday, then this doesn’t work since Louise and Grecia can’t go together, so you would have the two 2nd shift Louises on one side forcing the two first shift Grecias on the other, but this can’t be since there needs to be at least one shift in between. This leaves only Monday and Thursday for the H/J pairing.
Step 3. Draw out the H/J pairing on Monday. This makes it easy to place the two 2nd shift Louises into Wednesday and Thursday, and bookend them with the 1st shift Grecias on Tuesday and Friday, giving us the placement of every variable, again with H/J being interchangeable.
Step 4. Draw the second scenario mentioned above with the H/J pairing on Thursday. This shows us that the consecutive 2nd shift Louises have to be Monday Tuesday or Tuesday Wednesday. If you draw each of these out you’ll find that Tuesday has to be Katya in the 1st shift and Louise in the 2nd. Also, that Monday and Wednesday have to be a 1st shift Grecia and a second Shift H/J and a 1st shift H/J and second shift Louise. This also confirms that Friday has to be a 1st Shift Grecia a second shift Katya in both diagrams.
Once you realize there are only three possible diagrams for the entire game (when using H/J interchangeably) then you can absolutely zoom through this one and eliminate a lot of the confusion this game throws at you.
s_z says
Thank you so much for this!!!!
MemberGabrielle L says
This is an amazing deduction!
MemberShoney says
Hello. I teach an LSAT Prep course and tutor in Texas. This is in response to botched deductions on the re-attempt. I used a very similar setup as the one explained here, but one of my students actually found a way to solve it more quickly.
Three templates based on LL placement and you figure everything out. Bottom positions on Monday & Tuesday, Tuesday & Wednesday, and Wednesday & Thursday (game breaks if LL is placed on Thursday and Friday). Once you do that, all the other pieces fall into place (G+G placement in accordance to K being on Tuesday and Friday; one H/J together; and the other H and J separately in alternating spots).
Turns out the no two students together rule is fluff, and the H/J being together “more than once” is meant to throw you off since it always only happens once.
Once you understand the rules and limitations of the game, three templates should take about two or three minutes to draw and then you can answer every question is thirty seconds or fewer by simply matching.
Brittany says
Hi, I’m really appreciating this site. I just want to let you know that there is an error on this diagram (LSAT 76, Game 3 Setup, Gallery). On your main diagram the K in front of line 1 should be an L Not Law. Thanks!
TutorLucas (LSAT Hacks) says
Yes, that’s correct. Thanks for catching this! The page will be updated shortly.