by ohthatpatrick Sat Mar 10, 2018 8:11 pm
Hey, Liz.
For most questions in Games there is both a "clever" way to do it and a "brute force" way to do it.
If you know the "clever" way, take it! If you just "see" the answer, pick it!
If you don't, get going on "brute force". My success on this section of the test has almost always been "brute force". As soon as I'm not sure of what to do or what to think, I just start writing hypotheticals, and those give me all the ammunition I need to get all the answers right.
So I would recommend that you embrace the challenge of getting faster/smoother with brute force, because he's the type of friend that doesn't betray you when the stress of a real test makes it harder to be 'clever'.
In terms of the problem with how you approached Q22, it seems like you don't know the fundamental difference between the two types of ideas.
1. COULD BE TRUE / MUST BE FALSE = possible vs. impossible
To check whether an answer is possible, we try to write a scenario that matches the answer.
2. MUST BE TRUE / COULD BE FALSE (rare) = unavoidable vs. avoidable
To check whether an answer is avoidable, we try to write a scenario that DOESN'T match the answer.
Your first possible scenario was LMJFGKH
Eliminate (A), because having F on 3 is avoidable.
Eliminate (C), because having J on 4 is avoidable.
We can't use LMJFGKH to eliminate B/D/E, because those three answers match our scenario. Our scenario shows that B/D/E are possible. We only can assess whether they're mandatory or avoidable by trying to find counterexamples.
by the way, why would you pick (D), if your scenario also matched (B) and (A)?
L - F - GK
M - J
If we're analyzing (B), we're thinking, "Does H have to be last? Could someone else go last?"
GK are locked into 5 and 6.
__ __ __ __ G K __
We know we have L - F - GK,
so the only leftover pieces are M, J, and H.
Since we have M - J rule, we can't put M last. Thus, the only person besides H that could be last would be J.
__ __ __ __ G K J
This would force M/H __ __ H/M to be split up onto 1 and 4.
M/H, __ , __ , H/M, G, K, J
When you try to insert L - F - GK, you have to put L into 2 and F into 3.
M/H, L , F , H/M, G, K, J
But that breaks the rule that L can't be in 2. So by trying to find a counterexample to (B), we found out there ARE no counterexamples, which tells us that this answer must be true.
It's often hard at that final moment on Must Be True brute forcing: "This counterexample scenario I just tried blew up --- so, that means the answer is correct?"
Yes!
If you feel uncomfortable with that process, then you can defer on (B) when it seems like a counterexample ain't happening, and move onto (D) or (E) with that scenario you had:
LMJFGKH
For (D), can we move anyone else to spot 1? Sure, we could do
M J L F G K H
That eliminates (D) and, as it happens, also lets us eliminate (E).
Hope this helps.