# Which one of the following must be true?

kearann on July 24, 2020

I'm not sure how to diagram this question or even how to go about it?

Replies

Skylar on July 26, 2020

@kearann, happy to help!

Here is a video explanation of the original game setup that you may find helpful: https://testmaxprep.com/lsat/lsat-practice-videos/logic-games/lsat-prep-test-2-october-1991-game-2-setup

In this particular question, we are asked to identify the answer choice that must be true. To do this, we should go through each answer choice and try to create a scenario in which the arrangement described is NOT true. If doing so leads to a viable scenario, the answer choice is not necessarily true and therefore incorrect; if doing so fails to lead to a viable scenario, the answer choice must be true and is correct.

Answer choice (B) says "If O lives on the second floor, then L does not live on the fourth floor." To test if this must be true, we should create a scenario in which O is on the second floor and L is on the fourth. This gives us:
5:
4: L
3:
2: O
1:

What do our rules say about what we have placed so far? Rule #3 says that floor two only has one apartment. Rule #6 says that L is the only apartment on her floor. Therefore, we cannot assign any other residents to floors 2 or 4 in our scenario.
5:
4: L|
3:
2: O|
1:

Now that we have closed off those floors, we can move on to assigning the other residents. This is where we will run into a problem. Rule #2 says that K must be on the floor directly above P. However, there are no open floors left that are directly above each other. Therefore, it is impossible to have O on the second floor and L on the fourth. This means that (B) must be true, so it is our correct answer.

Does that make sense? Please let us know if you have any other questions!

charnsidhu17 on October 16, 2020

Hi, what is the best way to approach a question like this? Specifically, is it worth the effort to diagram all the scenarios?