This is an explanation of the fourth logic game from Section III of LSAT Preptest 77, the December 2015 LSAT.
Three volunteers out of five people will be assigned to three community committees (X, Y, Z). The volunteers are Haddad, Joslin, Kwon, Molina, and Nash (H, J, K, M, N). Each of the volunteers will have one of three positions – leader, secretary, or treasurer.
This one of the most “classic” games I’ve seen in recent years. If you approach it using only the rules, it’s extremely difficult. However, if you make a few upfront deductions, it’s very easy. This kind of game used to be very, very common. Now they’re rare. The first three games from this test are more typical: two rules based games, and a “weird” game.
However, it’s useful to practice the old games because they’ll let you breeze through classic games like this. Let’s look at how to set up the game.
First, and this comes from experience, it’s most useful to set this game up vertically. There are many past games that follow this format. You’ll see why this is best as we add deductions:
Next, don’t just go through the rules in order. Start with the easiest, clearest rules, and draw them directly on the diagram. Rule 1 says that Nash must be in leadership. We can draw this on the diagram by putting a
N below S and T:
Next, the fourth rule is clearest. It says that Joslin is the secretary for Y, but can’t be on committee X or Z:
Next, rule 3 places Kwon somewhere in Y, and says that Kwon can’t be in Z:
I’ve drawn K to the right of Y to indicate that they must go somewhere there. I’m saving the spots on the left for people who can’t go on a committee.
The final rule, rule 2, is that Molina can only be assigned to one committee. At first glance, it doesn’t seem like we can draw this on the diagram. But let’s stop and think about all the rules.
It’s always important to count numbers on logic games. Look particularly at the most restricted places. There are only five volunteers on this game, and each committee needs three volunteers.
Z is the most restricted committee: K and J can’t go there. That knocks 2/5 volunteers off the committee, so all the other three volunteers have to go to Z:
N, of course, goes in leadership. M and H are interchangeable between the other two roles. And we’re not done yet. Remember how rule 3 said that M can only go in one group? Since M is in Z, that means M can’t go in X or Y:
Now both M and J can’t go in X. This means that the other three all have to go in X: N, K and H
Once again, N is in leadership, H and K are interchangeable between the other two spaces. We’re more or less done, all that’s left is to note who goes in Y. Along with J, it will be K and one of N/H:
J is already in Y. K has to go in Y as well. M can’t, so the other space will be N or H. If N goes, obviously N goes in L. If H goes, then H and K can go in either spot.
So almost everything is determined in this game.
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: 5:01
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