Q4

[vincent.m]

Is there a key inference, or is it just plug-n-chug and luckily the first answer is right?

[hyemifaith6017]

This is how I answered this question.
I easily eliminated (B), (C), (E) because of the initial inferences I made.

My initial inferences show that Q can't be displayed 7th as W has to come after that so it allowed me to eliminate (B).
I eliminated (C) as RX has to be consecutive and there is no room for X if R goes to 3 and X at 5 isn't possible because R has to come before that and Q or T has to go at 4.
And I was down to (A) and (D).
I tried (A) and it worked and chose the answer.
I initially missed the inference that W can't go at 3.
If W goes at 3, because of the combination of 3rd and and 5th rule, Q has to go at 4, breaking the 1st rule. Q-W.

I hope this helps.

[christine.defenbaugh]

Excellent work, hyemifaith6017!

vincent.meyer, when faced with an unconditional question, before resorting to plug-n-chug, you want to make sure there aren't basic inferences you've missed.

Check out the original diagram. While we can't make a ton of inferences about where things can go, there are a handful of basic inferences to make about where things cannot go.



We know from Rule #1 that Q can't be 7th - eliminate (B).
We know from Rule #2 that R and X can't be 3rd and 5th, respectively, as the partner can never go in 4th - eliminate (C) and (E).

We might not have seen up front that W can never go 3rd, but you should be able to think that through without drawing an entire diagram around it, simply by asking yourself who could be 4th? Either Q is 4th, and W must come after it, or T is 4th and W can't be next to it. Neither scenario would permit W to be 3rd.

When you are down to (A) and (D), what's critical is not to waste a ton of time trying to prove that (A) can work. There are a handful of ways it could possibly work, but convincing yourself it's valid can be unnecessarily time consuming. The more efficient attitude is to glance at (A), and ask yourself 'is there anything preventing this?' Only carry the mental hypothetical a step or two before moving on to check (D).

One of the two will work, and one is a rule violator. Proving that (D) can't work is way easier than proving (A) can. The key is to move to that task quickly, eliminate (D), and confidently move on to the next question.

I hope that helps you strategize!