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- Thu Sep 21, 2017 2:50 pm
#40011
Complete Question Explanation
(The complete setup for this game can be found here: lsat/viewtopic.php?t=12912)
The correct answer choice is (C)
This is the infamous Rule Substitution question, a staple in the Logic Games section as of late. Considering their growing popularity, tackling such questions is no longer merely optional: it is imperative to have a workable strategy in place. Although the difficulty of this question may have been compounded by the fact that it was the final question in the section, a closer look reveals that the correct answer choice (C) is a straight restatement of the rule in question. Do not assume that the Rule Substitution question will necessarily be difficult! If you skip such questions by default, you may be robbing yourself of an easy point.
The question stem asks you to replace the fourth rule of the game, according to which if K is not assigned to Thorne, then both H and M must be assigned to Thorne:
Our job is to substitute that rule with a logically equivalent condition, which would have the exact same effect on the order in which the houses are shown. While the wording of the correct answer can be difficult-to-impossible to predict, the four incorrect answer choices will either present rules that were not part of the original rule set (also known as Additional Effects conditions), or else they will only partially constrain the variables in the rule being substituted (i.e. Partial Match conditions).
Since Additional Effects are easier to spot, look for answer choices that contain such conditions first. Unfortunately, none of the answer choices contains Additional Effects.
Answer choice (A): This rule establishes the following conditional relationship between K, H, and M:
This relationship is true given the original rule, according to which K’s assignment to Silva requires H and M to be assigned to Thorne, and not to Silva. The rule in answer choice (A), however, requires a lot less than the original rule: according to the former, as long as H and M are not both assigned to Silva, the rule is satisfied. This leaves open the possibility that one of H or M is assigned to Silva but not the other, or else that one of them is unassigned. Both possibilities are explicitly ruled out by the original rule. Furthermore, unlike the original rule, the sufficient condition in answer choice (A) fails to specify what must be true if K is unassigned. For these reasons, answer choice (A) contains a Partial Match and is therefore incorrect.
Answer choice (B): This rule establishes the following conditional relationship:
Furthermore, unlike the original rule, the sufficient condition in answer choice (B) fails to specify what must be true if K is unassigned. For these reasons, answer choice (B) is a Partial Match condition, and is therefore incorrect.
Answer choice (C) is the correct answer choice. This rule establishes the following conditional contrapositive (we jumped right to the contrapositive for the sake of convenience):
This condition is consistent with our original inference that F, H, and M must all be assigned to Thorne if K is not. Answer choice (C), therefore, does not contain an Additional Effects rule. The better question is: does answer choice (C) contain a Partial Match? It does not, because F and H must be assigned to the same group as each other (first rule). Thus, the effect of this rule is identical to that of the original rule, and both lead to one and the same inference:
Answer choice (D) establishes the following conditional relationship:
This relationship is clearly true given the original rule set, because whenever K is in Silva, H and L are not assigned to the same ceremony as each other. See Template 1. And inversely, whenever H and L are together, K is in Thorne (Templates 2A and 2B). However, unlike the original rule, the sufficient condition here does not mandate that H and M are both assigned to Thorne. For instance, the following hypothetical setup would be possible with this restraint in effect:
Answer choice (D) is therefore a Partial Match condition, and is incorrect.
Answer choice (E) establishes the following conditional relationship:
This condition clearly falls short of the original mandate requiring both H and M to be assigned to Thorne. Thus, answer choice (E) is also a Partial Match condition.
(The complete setup for this game can be found here: lsat/viewtopic.php?t=12912)
The correct answer choice is (C)
This is the infamous Rule Substitution question, a staple in the Logic Games section as of late. Considering their growing popularity, tackling such questions is no longer merely optional: it is imperative to have a workable strategy in place. Although the difficulty of this question may have been compounded by the fact that it was the final question in the section, a closer look reveals that the correct answer choice (C) is a straight restatement of the rule in question. Do not assume that the Rule Substitution question will necessarily be difficult! If you skip such questions by default, you may be robbing yourself of an easy point.
The question stem asks you to replace the fourth rule of the game, according to which if K is not assigned to Thorne, then both H and M must be assigned to Thorne:
Our job is to substitute that rule with a logically equivalent condition, which would have the exact same effect on the order in which the houses are shown. While the wording of the correct answer can be difficult-to-impossible to predict, the four incorrect answer choices will either present rules that were not part of the original rule set (also known as Additional Effects conditions), or else they will only partially constrain the variables in the rule being substituted (i.e. Partial Match conditions).
Since Additional Effects are easier to spot, look for answer choices that contain such conditions first. Unfortunately, none of the answer choices contains Additional Effects.
Answer choice (A): This rule establishes the following conditional relationship between K, H, and M:
This relationship is true given the original rule, according to which K’s assignment to Silva requires H and M to be assigned to Thorne, and not to Silva. The rule in answer choice (A), however, requires a lot less than the original rule: according to the former, as long as H and M are not both assigned to Silva, the rule is satisfied. This leaves open the possibility that one of H or M is assigned to Silva but not the other, or else that one of them is unassigned. Both possibilities are explicitly ruled out by the original rule. Furthermore, unlike the original rule, the sufficient condition in answer choice (A) fails to specify what must be true if K is unassigned. For these reasons, answer choice (A) contains a Partial Match and is therefore incorrect.
Answer choice (B): This rule establishes the following conditional relationship:
K S 
L S
Furthermore, unlike the original rule, the sufficient condition in answer choice (B) fails to specify what must be true if K is unassigned. For these reasons, answer choice (B) is a Partial Match condition, and is therefore incorrect.
Answer choice (C) is the correct answer choice. This rule establishes the following conditional contrapositive (we jumped right to the contrapositive for the sake of convenience):
This condition is consistent with our original inference that F, H, and M must all be assigned to Thorne if K is not. Answer choice (C), therefore, does not contain an Additional Effects rule. The better question is: does answer choice (C) contain a Partial Match? It does not, because F and H must be assigned to the same group as each other (first rule). Thus, the effect of this rule is identical to that of the original rule, and both lead to one and the same inference:
Answer choice (D) establishes the following conditional relationship:
This relationship is clearly true given the original rule set, because whenever K is in Silva, H and L are not assigned to the same ceremony as each other. See Template 1. And inversely, whenever H and L are together, K is in Thorne (Templates 2A and 2B). However, unlike the original rule, the sufficient condition here does not mandate that H and M are both assigned to Thorne. For instance, the following hypothetical setup would be possible with this restraint in effect:
Answer choice (D) is therefore a Partial Match condition, and is incorrect.
Answer choice (E) establishes the following conditional relationship:
This condition clearly falls short of the original mandate requiring both H and M to be assigned to Thorne. Thus, answer choice (E) is also a Partial Match condition.
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