#18 - Local, Not Necessarily True, False to True

[Dave Killoran]

Complete Question Explanation
(The complete setup for this game can be found here: lsat/viewtopic.php?f=231&p=88698)

The correct answer choice is (E)

The question stem stipulates that a third batch is made on the same day as a first batch. The only day this could occur is Wednesday (one kind of cookie is made on Monday-Tuesday-Wednesday, and another kind of cookie is made on Wednesday-Thursday-Friday). This scenario could only occur Template #1, under the following partial solution:

G3-Q18-d1.png

P2 and P3 are not fully placed, but must be made on two of Wednesday, Thursday, and Friday.

Answer choice (E) is not necessarily true—both S3 and P3 could be made on Friday—and thus answer choice (E) is correct.

[catherinedf]

I'm having trouble with Question 18. How would I go about solving this using templates? Here's how I drew my templates:

( S )
( P, P )
O OP __ S S


or

( S, O )
___ ____ OP PS PS

Thanks for all your help!

Catherine

[Nikki Siclunov]

For Q18, I probably wouldn't use templates and instead draw up a local diagram.

First you need to decide which cookie batches are such, that one kind of cookie's first batch is made on the same day as another kind of cookie's third batch. The only cookies that can satisfy this requirement are Oatmeal and Sugar: O's third batch, and Sugar's first batch, can both be on Wednesday.

So the five days will look like this:

(O) (OP) (OS) (S) (S)

The only thing we don't know is what happens to the last two batches of P: they need to be on two of the following three days: Wednesday, Thursday, Friday. Therefore, it could be false that exactly one batch of cookies is made on Friday (it could be two).

[madisonzill]

Why does this question only pertain to O and S?

[Adam Tyson]

O and S are the only variables that can meet the requirement of the question, madisonzill.

The only way one cookie's third batch can be the same day as another cookie's first batch is if that happens in Wednesday. Tuesday can't be the day of a third batch and Thursday can't be the day of a first batch, so we have to meet in the middle.

Wednesday cannot be the day of P's third batch, because P cannot start on Monday due to the rule that O's 2 bath and P's first batch are the same day. It's obviously not S's third batch, because S's second batch is Thursday, so it has to be O's third batch. O therefore has to be Monday-Tuesday-Wednesday.

P's first batch has to be Tuesday, the same day as O's second batch, which means it must be S's first batch that's on Wednesday with O's third. Thus we get O on Monday, O and P on Tuesday, O and S on Wednesday, and S on Thursday and Friday. The only question that remains is on which two days are P's second and third batches. They can be Wednesday and Thursday, or Wednesday and Friday, or Thursday and Friday. Thus only answer E can be false: we do not have to have just one batch on Friday because we could have two batches that day, P and S.

So O and S are not the only cookies affected by the rule, but they are the only ones completely fixed in place by the local restriction. It's only P that has any flexibility.