LSAT 79, Logic Game 4, Question 18, LSATHacks

For acceptable order questions, go through the rules and use them to eliminate answers one by one.

Note that I use the rules themselves. I don’t use my diagrams for these questions. Reading the rules again for this question will help you memorize them, and it’s also more efficient.

Since this game is unusually tough, this “rules based elimination” approach only easily eliminates three answers. E takes some work to eliminate.

Rule 3 eliminates B. That rule says that one computer transfers the virus to both S and R. So, this means S can’t transfer to R….which is a transfer in this answer.

Rule 4 eliminates C. R or T must transmit the virus to Q.

Rule 5 eliminates A. T or U must transmit the virus to P.

Answer E is a hard one. Though, it’s longer to write than it is to understand, I think. I’ll put it in bullet points:

• Answer E has five computers.
• That means there is only one computer left to add
• S is the missing computer
• Rule 2 says S must transfer to another computer. In this answer, only U is a candidate for transfer (everything else already has received a transfer)
• So, S would have to transfer to U, but
• Rule 3 says whoever transferred to R must transfer to S.
• In E, P transfers to R. That means P must transfer to S too.

So, we have a contradiction here. S has to be in two places at once, which is impossible. S can’t both transfer to U, but then receive the virus from P later.

D is CORRECT. It violates no rules.

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