- Mon Oct 30, 2023 12:45 pm
#103847
Hi Andy,
It's important to diagram the rules exactly as they are given and keep the rules and inferences that you make based on the rules separate. This is especially true for Rule Substitution questions (such as Question 6) because often the correct answer to a rule substitution is simply an inference that you've already made by linking the rules. In other words, the correct answer produces the exact same setup/diagram as you originally had just by skipping right to the inference that the two rules produce.
In this game, the fourth rule should be diagrammed:
not T 1 -> R 1
and the contrapositive is
(not R 1 -> T 1)
In plain English, this is known as the "either/or" rule and basically says "either R is first or T is first." (Note that "either/or" on the LSAT means at least one. In this game, R and T can't both be first because the game tells us that only one product type will be on sale each week.)
In Rachel's diagram above, she wrote "R1 -> not T1." While this is certainly true, it is not technically part of this rule (and definitely not the contrapositive of this rule.) That statement is an inference that would be true of any variable in any spot in the diagram because each spot can only have one product. For example, I could write, "If M is week 3, then S (or any other variable) is not in week 3."
While you were absolutely correct in linking rules 3 and 4 to come up with the inference that if T7 -> R1, it's important to realize that this is an inference made from linking these 2 rules and not a rule itself. For example, if a question suspends one of these two rules, that inference is no longer valid.