Which one of the following could be an accurate list of three of the courses Alicia takes?

Sabina on August 19, 2019

Why Answer Choice is E

Hi I was wondering if someone could please explain how E is correct if S 9am---->no WH How can Statistics and World History be taken together?

4 Replies

Irina on August 20, 2019

It is possible to take statistics at 3 pm, then 9 am condition would not be apply. The only scenario when statistics must be taken at 9 am if one of the courses chosen is psychology, since it is not the case here, she could be taking the 3 pm statistics section.

Urbano on January 18 at 03:16AM

How do we know that is the statistics at 3pm and not the one at 9am. Both rules 3 and 4 imply Stats9am. The answer choice, itself, does not address which stats is taken. This is confusing.

Urbano on January 18 at 05:06AM

In addition, wouldn't it be more correct to say that since W - >NotS9am - >NoTP because we don't have statistics as a choice for answer choice C or D. Because if P is in, then statistics9am must be in per rule 4. Or can we just say that since P is in and no stats9am is in, on both C&D answers it violates rule 4, thus incorrect.
For answer choice E: if W is in then stats9am is out, however, doesn't meant stats3pm is out, so we can still have a stats. Russian being in doesn't trigger anything so its fine. Thus Russian, stats and world history can be the three chosen.

Skylar on January 19 at 04:07AM

@shenricus and @ulino23, happy to help.

First, let's look at the game setup:

G J M P R S(9)/S(3) WH

__ __ __ __ | __ __ __
IN OUT

Rule 1: Not R -> J
Not J -> R
So either J or R must be in, possibly both,
Rule 2: M -> Not J
J -> Not M
So J and M cannot both be in.
Rule 3: S(9) -> Not WH
WH -> Not S(9)
So WH and S(9) cannot both be in.
Rule 4: P -> S(9)
Not S(9) -> Not P
Combining Rules 3 and 4 gives us:
P -> S(9) -> Not WH
WH -> Not S(9) -> Not P
So WH and P cannot both be in.
Rule 5: G or WH must be in, BNB


Now, let's look at the answer choices:

(A) is incorrect because it has both G and WH in, which violates Rule 5.
(B) is incorrect because it has both J and M in, which violates Rule 2.
(C) is incorrect because the combination of Rules 3 and 4 show that, since P is in, S(9) must also be in, and WH must be out. However, here both P and WH are in.
(D) is incorrect for the same reason that (C) is incorrect.
(E) is correct because R S(3) WH (J/M) is a valid possible group of courses Alicia could take.

Note that Rules 3 and 4 only apply to S(9), not to S(3). In the scenario described in (E) the time of the statistics course is left open, meaning that we can pick whichever time works- which is S(3) in this case. Moreover in (E), Rule 5 tells us that we could not have G in, and the combination of Rules 3 and 4 show that we cannot have P in either. However, if either J or M fill the last "in" spot, the scenario is valid.

Does that make sense? Please reach out with any additional questions!