All Honor Roll students in Mr. Braiman's class after 2002 read To Kill a Mockingbird. All Honor Roll students in Mr. Braiman's class after 2006 read The Natural.
If a student read To Kill a Mockingbird but did not read The Natural, which one of the following MUST be TRUE?
(A) The student was in Mr. Braiman's class before 2007.
(B) The student was in Mr. Braiman's class after 2002 and before 2006.
(A) and (B) are both wrong because the two rules stated in the stimulus apply only to Honor Roll students. The question stem does not tell us whether the student in question is an Honor Roll student or not. The stimulus tells us nothing about non-Honor Roll students, so there is nothing that we can say MUST be true about any student unless he is an Honor Roll student. Both (A) and (B) could be true, but the question is what must be true. The fact that the other three answer choices expressly refer to Honor Roll students should have been a hint that this was a necessary condition.
(C) If the student was an Honor Roll student, then the student was in Mr. Braiman's class before 2007.
(C) is correct. This is the only one of the four choices that MUST be true. If the student was an Honor Roll student and did NOT read The Natural , then he cannot have been in Mr. Braiman's class after 2006, because if he was, he would have read The Natural. Therefore this student must have been in Mr. Braiman's class before 2007.
(D) If the student was an Honor Roll student, then the student was in Mr. Braiman's class before 2003.
(D) is incorrect because it can be true, but it can also be untrue based on the rules given in the stimulus. Nothing is mentioned in the stimulus regarding what Mr. Braiman's Honor Roll students read or did not read prior to 2003 (or 2007), so it is possible that the student in the question was an Honor Roll student before 2003 and did not read The Natural. However, it is also possible that an Honor Roll student in Mr. Braiman's class before 2003 did read The Natural. The fact that they all read it after 2006, which is the ONLY rule stated with respect to this title, does not mean or imply that none of them read it before 2007, let alone before 2003.
(E) If the student was an Honor Roll student, then the student was in Mr. Braiman's class after 2002 and before 2007.
(E) is incorrect because the stimulus does not tell us whether or not any of Mr. Braiman's Honor Roll students read To Kill a Mockingbird before 2003. It only tells us that after 2002, they all read To Kill a Mockingbird, which does not mean that none of them read it before 2003. Therefore the fact that the student in question did read To Kill a Mockingbird, assuming he was an Honor Roll student, does not necessitate that he was in Mr. Braiman's class after 2002.
Many people answered this question wrong by either ignoring the limitation of the rules to Honor Roll students, ignoring the fact that the question does not specify whether the student in question is an Honor Roll student or not, or making one very important, but very mistaken, inference: That the Honor Roll students read To Kill a Mockingbird only after 2002 and not before 2003.
The rules in the stimulus say none of this. Nor can this be reasonably inferred from either of the rules stated in the stimulus. This is why it is important to read the stimulus carefully, and consider each of the choices carefully. All of the four wrong answer choices could be true, but could also be untrue; only (C) cannot be true if the key condition, being in Mr. Braiman's class before 2007, were changed.
Remember also to use the contrapositive. If all Honor Roll students AFTER 2003 read To Kill a Mockingbird, that means that no Honor Roll student after 2003 did not read To Kill A Mockingbird. If all Honor Roll students after 2006 read The Natural, that means that no Honor Roll student after 2006 did not read The Natural. But that's all it means. What neither rule implies is that no Honor Roll student read either title BEFORE the associated dates. The main mistake that most people made was to infer that To Kill a Mockingbird had to have been read between 2003 and 2006. Not true.
You must be careful not to read into the stimulus anything that it does not say. Pay attention to what it does say, and to any reasonable inferences that can be drawn from it. Also pay attention to words like "all," "only," "always," "never," "none," etc. What do they require? (What must be true?) What do they rule out? (What cannot be true?) What do they allow? (What could be true?)
Here's another way to look at it:
RULE #1
WHO: all Honor Roll students in Mr. Braiman's class
WHEN: after 2002 (2003-present)
WHAT: read To Kill a Mockingbird
RULE #2
WHO: all Honor Roll students in Mr. Braiman's class
WHEN: after 2006 (2007-present)
WHAT: read The Natural
QUESTION:
WHO: student
WHAT: read To Kill a Mockingbird; did not read The Natural
APPLICATION:
Under what circumstances would either rule be violated?
- Neither rule applies if the student is not an Honor Roll student. If the rule does not apply, it can't be violated.
- The rule only applies if the WHO is satisfied. The question tells us the WHAT. Therefore the key condition is the WHEN.
- Rule #1, if it applies, can only be violated if the student in question did not read To Kill a Mockingbird. The student in question did read To Kill a Mockingbird, so Rule #1 is not violated regardless of when he read it. Even if he was in the class before 2003, the fact that he read this book at all prevents him from violating Rule #1, because he could have read it at any time. The rule is only violated if the conditions cannot satisfy the rule. In other words, even if the student read To Kill a Mockingbird in 1998, it can still be true that all of Mr. Braiman's Honor Roll students after 2002 read it as well.
- Rule #2, if it applies, can only be violated if the student did not read The Natural. The student in question did not read The Natural, therefore the rule is violated if the other conditions are met. Since all of the Honor Roll students in the class after 2006 did read it, he cannot have been in the class after 2006 if he didn't read it, and thus must have been in the class before 2007.
