June 2010 LSAT
Section 2
Question 16

# If the cargo bed is cleaned exactly twice, which one of the following must be true?

Replies

Jessica-Killeen on January 24, 2019

Please respondRavi on February 13, 2019

@Jessica-Killeen,Happy to help!

We know that those 7 configurations are the only 7 that can exist

because of our 2 rules:

1) Max 3 cleanings

2) M in 5

_ _ _ _ M _ _

The most important inference to draw in this game is that if there are

3 M pieces and 4 S pieces AND we can only have a maximum of 3

cleanings, then the M pieces cannot be spaced out individually because

if they were (as in, if they were in 1, 3, 5, and 7), then there would

be way too many cleanings.

From this, we know that the M pieces need to either go in a block

(MMM) or in a block of two and a single (MM with the the other M

somewhere).

You're right, this inference can take some time, but the benefit of

figuring it out and creating those boards is that the questions will

go by very fast.

We can answer this question without making all the different

scenarios. Let's see how that looks.

The question asks, "if the cargo bed is cleaned exactly twice, which

one of the following must be true?"

If there are two cleanings, then we know that there must be three

separate clusters of loads.

The important thing about this additional premise is that because we

know there are only 2 cleanings, we cannot have two groups of M

clusters because that would require a minimum of three clusters. In

other words, we can't have MM and M somewhere else. Thus, we now know

that the Ms all have to be together.

What's more, we know the Ms can't go in 5 through 7 because if they

did, then there would only be 1 cleaning.

From this, we know the Ms are either in 3 through 5 or 4 through 6.

_ _ M M M _ _

_ _ _ M M M _

(A) says that "the second load is stone." We know this must be true

given that we've placed all of the Ms already in this scenario (with

two cleanings), so yes, the second load must be stone. (A) is the

correct answer choice.

Does this make sense? Let us know if you have any more questions!