LSAT PrepTest 44 Section 3 Question 20 Explanation | Logic Games

I didn't write the following blog post. It was already on the blog when I took over the URL. The following blog post may contain mistakes. -Steve

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This Logic Games question is from the October 2004 LSAT.

We can use a table as our diagram for this question. It will be made up of the days of the week, Monday through Friday. Our symbols that we'll put into the diagram will be X, Y, and Z, the three lots, and the prices of each lot, since we don't yet know which price X and Y have. Let's make the table (R = Thursday) and fill it in with symbols, using trial and error and conforming to the rules in the set-up and the question:

M | T | W | R | F |

Z12 |Y10| Z12 |X15 | Y10|

I'll walk you through the trial and error a little more than usual, since we have two kinds of symbols, which makes it more complex:

1) We know Z = 12, and since X costs more, it must be = 15, and Y = 10.

2) Put 15 in the R spot, following the set-up rule.

3) Put Y in the F spot, since it's cheaper than Z, and put Z in the W spot, following the set-up rules.

4) Since Z must be used on more days than X, put it in on Monday and fill the final slot, T, with Y.

5) Check to see that all this still fits with the rules. It does.

Okay, now we proceed to the answer choices to eliminate some of them. Remember, since this is a must question, if any choice doesn't agree with our diagram, it's out, since that shows it doesn't have to be true.

A) Incorrect, doesn't fit our diagram.

B) Could be.

C) Incorrect, conflicts with diagram.

D) Incorrect, doesn't fit diagram.

E) Could be.

So, as is the case with many of these questions, we need to retool our diagram to eliminate one more answer choice. So, again using trial and error, we come up with another set-up that fits the rules (since there was no reason why we had to put Y on Tuesday, we can just switch Monday and Tuesday):

M | T | W | R | F |
Y10 |Z12| Z12 |X15 | Y10|

Now, we reevaluate B and E.

B) Wrong, doesn't fit diagram.

E) Correct.

Remember:

1) Make a diagram and put the symbols in it. A table will work for virtually any LSAT Game. It's fast, simple, and effective.

2) Use trial and error to make diagrams that fit the rules, and retool them when they don't eliminate 4 answer choices.

3) On must questions ("must be true," etc.) remember that if an answer choice doesn't agree with your diagram, you can eliminate it. After all, if it had to be true, and your diagram is right, it would have to agree with your diagram.