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Here's a Logic Games question from the December 2003 LSAT.
Our diagram can have a maximum of 2 batches on Monday. Why? Because we can't make peanut butter (PB) cookies until we make the 2nd batch of oatmeal (O) cookies. The earliest we can make the 2nd batch of oatmeal cookies Tuesday because you can't make more than one batch of a given type per day.
Because we don't know about the other days, we'll have to make a diagram.
In this diagram, we'll have several options because the rules aren't very restrictive. In the following diagram, we'll put the batches on as few days as possible to violate some choices above. We want to prove more than 2 batches can go on a certain day.
Let's put S on Monday, Thursday (as the rule says), and Friday. O will also go on Monday, Tuesday (so PB can start then), and Friday. PB will go on Tuesday (since it can't start until O is on its second batch), Thursday, and Friday:
Monday: O, S
Tuesday: O, PB
Wednesday:
Thursday: O, PB, S
Friday: PB, S
This fits the rules. Since we have placed more than 2 batches on two days (Thurs. and Friday), we can eliminate C and D. Now, let's alter our diagram to violate more choices. Let's try to prove Tuesday can have more than 2 batches by moving S's first batch to Tuesday:
Monday: O
Tuesday: O, PB, S
Wednesday:
Thursday: O, PB, S
Friday: PB, S
This fits the rules too, so C is out (there can't be 3 days on which at most 2 batches are possible, since we've shown that this is only possible on Monday and Wednesday). Now, we already know that there are, at most, 2 batches on Monday, but we aren't sure about Wednesday. Now, we'll need to alter our diagram one last time. We need to prove Wednesday can have more than 2 batches, so let's give it O, PB, and S:
Monday: O,
Tuesday: O, PB,
Wednesday: O, PB, S
Thursday: PB, S
Friday: S
This fits the rules, so we've eliminated everything but Monday. Only one day can have a maximum of 2 batches, so A is correct.
Remember:
1) Use a diagram with a table and symbols to eliminate answers (on paper, I'd draw this horizontally with the symbols above the days of the week, but it's much easier to write it this way on the blog). Think about the rules first and see if you can easily eliminate some choices before even drawing your diagram.
2) Alter your diagram to violate more answer choices. Any new diagrams might come in handy in future questions or answer choices. For this reason, never erase or cross out old diagrams.
its nice to see that you, who once did not suck at games, now does suck at them because it gives hope that I, who currently suck at the games, might not suck by october.
ReplyDeleteMy initial problem with this game was that I understood it as asking for the days IN A SINGLE WEEK in which at most two batches of cookies could be made on a single day. If you look at it that way, no matter how you set the game up you're always left with three days on which you can have two or less batches (which would make C the right answer). I completely misread this question...
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