LSAT 30, Game 3 Setup, Carwash, LSATHacks

LG Game 3 Setup, by LSATHacks

This is an explanation of the third logic game from Section I of LSAT Preptest 30, the December 1999 LSAT.

Five people – Frank, Marquitta, Orlando, Taishah, and Vinquetta (F, M, O, T, V) – had their cars washed one at a time. Each of the cars received exactly one kind of wash: regular, super, or premium (r, s, p). You must determined the possible sequence based on the rules.

Game Setup

This game is a mix of sequencing and grouping. The rules tell us the order the cars are washed in, and they also tell us which type of wash each car receives. 

It doesn’t really matter exactly what you call this type of game. I’ve never seen seen another quite like it. The most important thing is representing the rules in a way that makes sense, and combining them.

Here’s how to draw the first two rules. The first wash isn’t supreme, and only one wash is premium:

(It’s easiest to draw the wash types under the diagram)

You need a quick way to remember that 2 and 3 will always be the same. I find an arc joining the two works well:

The next two rules are sequencing rules. V is before O and T:

And M is between O and F:

V goes first. There are only five cars, and T, O, M and F all come after V.

The fifth rule tells us (among other things) that there will always be at least some regular washes. So all three wash types have to be used: s, p and r.

Some people stop there, but we’re not done yet. It’s always worth looking at your most restricted variable and seeing whether you can make deductions.

In this case, M has two rules. M is between O and F, and the car directly in front of M has a regular wash.

We can only put M in two places. They can go third if T goes afterwards, or they go fourth if T goes beforehand. We should try both and see what happens.

Here’s what happens if M goes third:

We need at least one super, and exactly one premium.

If M goes fourth, things are still pretty restricted. Car three has to get a regular wash, because the car in front of M always gets a regular. 

Car’s 2 and 3 always get the same wash, so car 2 is also regular.

There’s more. Car 5 is the only car left that can get a super wash. That leaves car 1 to be the car that gets a premium wash.

You’ll notice that O has to get a regular wash in both scenarios. This always has to be true, and that deduction answers question 15.