### Game Setup

**Time on first attempt: **11:37

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There’s no way around it. This is a very hard game. I’m not even sure what type to call it.

The best way I know of to solve it is to make a rough structure, and then flesh it out on individual questions. I’m not sure quite how to put it, but the diagram should clarify what I am referring to. It would be a mistake on this game to try to map out all possibilities in advance: there are too many.

I made one mistake on this, by the way. I should have made zero, but I had less time than I wanted because I went very slowly on game 2. (I got interrupted in the middle of game 2, so I’m not sure whether that game was really hard, or whether it was the interrupt which caused the problem.) With 30-40 more seconds I think I would have gotten all the questions on game 4. I do often spend 12 min or so on one hard game, if I’ve gotten through the others quickly enough.

**Diagrams**

Enough preamble. Here’s what I drew for this one:

This combines rules 2 and 3. The blank spaces show that *some *computer transmitted to R and S, but we don’t know which one did. Likewise, the blank space after S shows that S transferred to *some *computer, but we don’t know which one.

Next, I drew these two diagrams for rules 4 and 5:

These show that *one *of the preceding computers transferred the virus. (Only one computer can transfer). So, either R or T transferred to Q, but *not *both.

A note on how to use these: on some questions, you’ll end up with a scenario where, for example, T transfers to R, only. What does that let us prove? Well, T was also an option for Q and P. But, since T doesn’t transfer to them, that means you can also say that “R transfers to Q” and “U transfers to P”, because those were the only options that weren’t T on the two diagrams above.

So, the main method I used on this game was to quickly glance between the three diagrams, and figure out if a change on one necessitated a change on the other two. I don’t know of a better method. If I think of one after repeating this game a few times, I’ll update this explanation. But, there may be none – this is a hard game. But knowing that there are really only three main rules to look at simplifies things.

Note: you must also remember one rule. No computer transfers more than twice. You should also remember that there are only six computers. So, the first diagram is actually more complete than it seems. It pictures four computers. Two of them are blank, but this at least gives us a skeleton structure for the order.

**Only T and U can go first**

This wasn’t a deduction I added to the diagram, but I think it’s important to know. The computer that goes first can’t be on the right hand side of a transfer. And, if you look at the setup, you’ll see that:

- R and S get a transfer from an unknown computer
- Q gets a transfer from R or T
- P gets a transfer from T or U

So, R, S, Q and P can’t go first. Only T and U are left!

I didn’t actually draw this, because I found there were too many branching diagrams. But, it’s still helpful to *know *that only T or U can go first.

**How the virus transfers**

Apart from the rules, you need a high level model of what’s happening in the game. This isn’t super complicated, but if you start without one, it’s disastrous.

So:

- We have a computer network, uninfected
- A virus arrives from somewhere, into a single computer
- That computer transfer the virus to either 1 or 2 computers
- Every other computer transfers to 0, 1 or 2 other computers, until everything is infected
- A transfer only happens
*between two*computers. As in, you can’t have to computers transfer into a single other computer. So you can’t have RT transfer to Q. Instead, either R does, or T does, alone.

Again, none of these are complicated, but this is the sort of thing you must sort out when you see a new game type. It’s worth spending more time upfront to be clear on what’s happening.

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Immanuel says

This was so helpful, went at it a second time and I was able to get all the answers correct, as opposed to my first attempt which I was only able to get 3 correct.

Thank you!!

TutorRosalie (LSATHacks) says

Thank you!

Ken says

On my second attempt, I drew solid lines between elements we knew about (i.e. __ -> R and S, S -> __), and dotted lines between elements that were possible (e.g. T – – > P and Q). From there I realized that since each computer received the virus only once, we can move forward with one of the dotted lined options, and solidify the other dotted line choices (e.g. if R->Q, then T->P, and U is a free element). This allows you to make 4 different scenarios. Unfortunately I can’t write up the scenarios effectively in this format so I’ll have to display them linearly:

Scenarios 1 and 2 (if R -> Q)

*** -> R -> Q

*** -> S -> __

Options to put in *** and __: T->P and just U or U->P and just T

The other scenarios would be “R not to Q” (i.e. T -> Q or T -> P and Q) and go from there.

TutorRosalie (LSATHacks) says

That works as well!

Eric says

Hello! Just a small grammar thing.

I think you meant ‘two’ in the sentence: “As in, you can’t have to computers transfer into a single other computer. ”

Thank you so much for these explanations! Its truly a wonderful resource