LG help: PT59 S1 Q10

vamos
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Joined: Sat Jan 15, 2011 2:50 am

LG help: PT59 S1 Q10

Postby vamos » Tue Mar 08, 2011 11:56 am

I'm having trouble approaching these question types that appear in the newer logic games: Which one of the following , if substituted for (insert rule), would have the same effect?

I spent alot of time on this question and still missed it. I don't really have a plan of attack when I have a question like this. I'm not sure what I'm supposed to be looking for. Any advice on how to approach them?
Last edited by vamos on Tue Mar 08, 2011 1:24 pm, edited 1 time in total.

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Jack Smirks
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Re: LG help: PT59 S1 Q10

Postby Jack Smirks » Tue Mar 08, 2011 12:36 pm

vamos wrote:I'm having trouble approaching these question types that appear on the newer logic games: Which one of the following , if substitued for (insert rule), would have the same effect?

I spent about alot of time on this question and still missed it. I don't really have a plan of attack when I have a question like this. I'm not sure what I'm supposed to be looking for. Any advice on how to approach them?

Here's a good discussion: viewtopic.php?f=6&t=117641

tomwatts
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Re: LG help: PT59 S1 Q10

Postby tomwatts » Tue Mar 08, 2011 12:45 pm

See the various links in this topic for details on this question type. (Was beat on the link; same as above.)

For this specific question, the rule in question is that H is not first and H is before K. Now, we know from the first clue that G and K are related elements — they're next to each other — so our best bet is that the right answer is going to have something to do with G. Only B and D have to do with G, so it's probably one of those. It's not B, because we know that something other than F or M could be first; for example you could have L I M H G K F, which would put L first. B therefore makes something impossible that was possible before.

D, on the other hand, works: if H is not second, then it's between M and G. M, we know, is one of the first three; if H is third or later, M is before it, which means that H is after it, and H being before G also puts it before K, as before. If H is second, then, well, it's before K anyway (because K is not first — it needs G before it), and it's not second. Thus, it has an equivalent effect.

vamos
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Re: LG help: PT59 S1 Q10

Postby vamos » Tue Mar 08, 2011 5:30 pm

Thanks for the link, it was very helpful.

As for this particular question, I simply skipped answer choice (D) because the wording is confusing, it has 2 necessary conditions: unless H2, it must be between M and G. What is the proper diagram for a statement with two necessary conditions and no sufficient condition?

tomwatts, what was your reasoning for diagramming this statement as ~H2 --> M-H-G? You chose to diagram what followed unless as the sufficent condition and you negated it. In that sense, it seems like the proper way to diagram a statement with two necessary conditions and no sufficient condition is to select one of the necessary conditions and convert it into a sufficient condition + negate it.

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EarlCat
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Re: LG help: PT59 S1 Q10

Postby EarlCat » Tue Mar 08, 2011 6:41 pm

vamos wrote:Thanks for the link, it was very helpful.

As for this particular question, I simply skipped answer choice (D) because the wording is confusing, it has 2 necessary conditions: unless H2, it must be between M and G. What is the proper diagram for a statement with two necessary conditions and no sufficient condition?

Think of how necessary conditions are changed into (negated) sufficient conditions when writing the contrapositive.

In ~A-->B, B is necessary. In the contrapositive, ~B-->A, ~B is sufficient. So for "You must have A unless you have B," either A or B can be negated and used as the sufficient for the other.

Same thing here. Either H2 or M-H-G can be negated and used as the sufficient condition for the other.

tomwatts, what was your reasoning for diagramming this statement as ~H2 --> M-H-G? You chose to diagram what followed unless as the sufficent condition and you negated it. In that sense, it seems like the proper way to diagram a statement with two necessary conditions and no sufficient condition is to select one of the necessary conditions and convert it into a sufficient condition + negate it.

The simplest way to look at it is to replace "unless" with "if not."

If not H2 (i.e. if H is not 2) then H must be between M and G.
~H2 --> M-H-G

I haven't looked at the game, but if there's not a rule that M is before G, make sure you indicate that M-H-G could be reversed.

vamos
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Re: LG help: PT59 S1 Q10

Postby vamos » Tue Mar 08, 2011 9:19 pm

After further reviewing, I have a much better understanding. There's two ways of diagramming unless statements:

A unless B (~A --> B)

or

If not B, then A (~B --> A)

I was used to diagramming unless statements in the first form, but this problem is a good example of why it's good to practice both.

As EarlCat stated, It would have been more simple to use the second form: If not H2 --> M-H-G.

Thanks for all the responses!




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