In/Out Games

jocelyne
Posts: 160
Joined: Tue Nov 11, 2008 4:15 am

In/Out Games

Postby jocelyne » Sat Jan 30, 2010 3:22 pm

Can someone explain to me how to do these? I still don't seem to get these. What's the best strategy? The Atlas technique is confusing...and I don't know what to do once I get the set of diagrams from LGB.

Do I just go straight to the questions? Work out hypotheticals? Anyone care to diagram the bird game? Thanks!

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chewdak
Posts: 106
Joined: Fri Apr 03, 2009 5:54 pm

Re: In/Out Games

Postby chewdak » Sat Jan 30, 2010 3:33 pm

jocelyne wrote:Can someone explain to me how to do these? I still don't seem to get these. What's the best strategy? The Atlas technique is confusing...and I don't know what to do once I get the set of diagrams from LGB.

Do I just go straight to the questions? Work out hypotheticals? Anyone care to diagram the bird game? Thanks!


Came across http://www.griffonprep.com/Birdgamesolution.html the other day.
Hope it helps.

Cambridge LSAT
Posts: 270
Joined: Mon Aug 24, 2009 3:26 pm

Re: In/Out Games

Postby Cambridge LSAT » Sat Jan 30, 2010 3:46 pm

The Atlas technique is actually very effective if mastered. It does take a bit of practice in order to internalize, and it does have a couple minor limitations. Sufficient conditions containing the word and (A and B --> C) along with necessary conditions containing the word or (A --> B or C) can be difficult to incorporate into the main diagram. You might want to note such conditions off to the side. If you're not using this system, consider chaining together some of the rules before heading to the questions. That's where the Atlas technique comes in handy. Most of the chains will be in place just by adding the arrows to the diagram.

Keep in mind that not all in/out games are created equal. For instance, the fourth game on PT 58 doesn't lend itself to linkage in the standard way. Some in/out questions draw on number limitations more than linked conditions.

dakatz
Posts: 2460
Joined: Sat Mar 29, 2008 4:19 pm

Re: In/Out Games

Postby dakatz » Sat Jan 30, 2010 3:54 pm

I tutor this game pretty often, because many people seem to have trouble with in/out games. The key is to NOT jump right into the game right after you write down the rules. The beauty of in/out games is that all rules can be combined to make one long chain of deductions that clarify and simplify the whole game. Not all people do it this way, but I find it very helpful. Here are the main rules with their contapositives (the dash before a letter stands for "not"

1. H ---> -G , G ---> -H

2. J or M ---> H , -H ---> -J and -M

3. W ---> G , -G ---> -W

4. -J ---> S , -S ---> J


Look for common factors that can be combined. Remember that you can combine the positive form of one statement with the contrapositive of another.

Lets start with rule 2.

J or M ---> H ---> -G

So we took rule 2 and combined it with rule 1. But we can keep adding to this chain.

J or M ---> H ---> -G ---> -W

And finally, we know that -S leads to J, so we can add that onto the beginning of the chain.

-S ---> J or M ---> H ---> -G ---> -W

Just keep in mind that the -S just leads to J. Sometimes, I will write the -S arrow as a diagonal pointing to J because I want to remind myself that -S will never inherently give me M in the phrase "J or M". The post above me has a good way of diagramming this, with a separate leg for the M, thus clarifying the -S --> J --> H leg. Whichever way works, they both mean the same thing.

Now, write the contrapositive of that long chain, and you will have all the info you need to do the game.

W ---> G ---> -H ---> -J and -M ---> S

Again, I write the S arrow as a diagonal coming out of the -J just to remind myself that -M has no relationship to S, only the -J does.

With these two chains, the game is very easy because you can see exactly what happens when any single factor is picked. All 6 birds are accounted for the chain. Hope this helps!




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