Rule substitution questions are easier than they seem. There are not many ways the testmakers can create the same effect with a new rule.
Usually, the testmakers will use the secondary effects of a rule. For instance, in this case, rule 1 says that FH are together. So when rule 4 forces H to go into T, really it means that FH must go to T.
This means that you can duplicate the rule’s effect by referring to F instead of H. Only C mentions F.
If you look closely, the effect is the same. Instead of forcing H and M into T, K forces F and M into T if K isn’t assigned to T. Because F and H go together, this new rule forces H into T as well. C is CORRECT.
All of the wrong answers make one of these two mistakes:
- They allow things that aren’t normally allowed.
- They ban things that aren’t normally banned.
Some of the wrong answers are true according to the normal rules. But you’re not looking for what’s true. You’re looking for something to replace the effect of the missing rule.
A is wrong because it allows one of H or M to be assigned to S with K. Normally this can’t happen.
B is wrong because it doesn’t say where F, H and M must go.
D is wrong because it doesn’t force M to be assigned to T if K isn’t assigned to T.
E is wrong because it should have said “unless both H and M are assigned….”
Want a free Logic Games lesson?
Get a free sample of the Logic Games Mastery Seminar. Learn tips for going faster at logic games
MemberGabrielle L says
I know there are a bunch of tricks for diagramming “unless” statements, but I would like to understand what these statements actually mean to solidify my understanding and make sure I don’t mess up the rules. So take this sentence:
“Unless Knutson is assigned to the Thorne University ceremony, both Frost and Mays must be assigned to that ceremony.”
Here’s the LSAT rule I’ve heard – When you see an unless statement, negate what comes before “unless.” So here – “Both Frost and Mays are assigned to the T ceremony unless K is assigned to it” means ” not F or M -> K.”
But when I read the original statement, I think – “If K goes to Thorne’s ceremony, then F and M can’t be there.” Which makes me want to write “K -> not F and M.” I don’t see how this is an issue since the statement says the presence of K means F and M can’t be there, but that doesn’t seem to be right.
What am I missing here? And thank you in advance!
FounderGraeme Blake says
It’s true that what is before unless is what you negate, but the funny thing about English is you can entirely reverse a sentence and it has the same meaning. Both of these mean the same thing.
1. Unless Knutson is assigned to the Thorne University ceremony, both Frost and Mays must be assigned to that ceremony.
2. Both Frost and Mays must be assigned to that ceremony, unless Knutson is assigned to the Thorne University ceremony
In the first example, there is *nothing* before unless, so you can’t apply that rule literally. You have to translate it to the second format to apply it mechanically. You get “not F or M -> K” either way.
I guess a more precise rule would be: The thing after the unless is necessary. The other part of the sentence is sufficient, but negate it.
But that’s too clunky.
Really though, what you should do is this: take a simple sentence you can never get backwards, and play around with it until you get unless intuitively
1. Unless you have a tail, you’re not a cat
2. You’re not a cat unless you have a tail
You know how cats work. You know how tails work. Play around with these by making examples and counterexamples until you understand unless on a gut level. That’s the real way.
Wonhee says
Hi Graeme, thank you for all your help. I see how answer C is obviously correct, but I’m having a hard time seeing why answer E is not correct. I notated this rule as follows: “H(notT) or M(notT) –> K(T).” Isn’t this the exact contrapositive of the original rule: “K(notT) –> H(T) and M(T)”?
MemberAbhishek Makam says
Why doesn’t De Morgan’s rule apply to option E?
Original rule: If not K(t), then H(t) and M(t)
Contrapositive with De Morgan’s: If not H(t) or not M(t), then K(t)
E, essentially spells out this contrapositive.