Hard Games Question: Superprep, 2nd Test, 2nd Game, Trees in Park. Help!

[Jack Daws]

Jeffort, I mentioned in that other reply that I'd find an example of the kind of game that twists me in knots. This Trees game is just confusing and I couldn't finish it. And the explanation in the Superprep book isn't all that helpful. Sure, it tells you why, but it doesn't giver you any tips on how to break it down from the beginning or make a diagram. Grrr!

[Jeffort]

Jeffort, I mentioned in that other reply that I'd find an example of the kind of game that twists me in knots. This Trees game is just confusing and I couldn't finish it. And the explanation in the Superprep book isn't all that helpful. Sure, it tells you why, but it doesn't giver you any tips on how to break it down from the beginning or make a diagram. Grrr!

Yeah, that one seems to have been written by the

This game is a lot like the birds in the forest game (Dec 2000) on steroids.  It's one of those in/out grouping games.

Interpreting what the 3rd and 4th rules mean properly, as well as linking up the contrapositive of the last rule to the not both part of the 3rd rule is the key to the game.

Rule 3:

Y   L or O

The Not both part of rule 3:

L & O   Y

link that with the first rule

L & O   Y   M

Rule 4:

L OR O    F & S

take the contrapositive of it:

F or S      L & O

Link that with the result from rule 3 and you get:

F or S   L & O Y  M

That chain takes out questions 10, 11 and 12 with ease and helps a lot on questions 8 and 9.

If you don't get that stuff together the game is a giant time trap that tries to burn you out while you write hypos all over the page and get really frustrated and feel like  

If you make rule 4  L AND O (instead of OR)    F & S the whole thing falls apart.

Hope this helps!
 
 

[Jack Daws]

Haha, nice chewbacca!

Let me take a look at that game again with those diagrams in front of me and see how it goes this time.

Thanks for the help!!!!!!!! 

[Ashley O]

Rule 4:

L OR O    F & S

take the contrapositive of it:

F or S      L & O

I don't understand how you did this. How does it go from and to or when you take the contrapositive? shouldn't there be a negative or something in there?

[Jeffort]

Rule 4:

L OR O    F & S

take the contrapositive of it:

F or S      L & O

I don't understand how you did this. How does it go from and to or when you take the contrapositive? shouldn't there be a negative or something in there?

Yeah, something screwed up with the BBC code and the strike through negatives didn't display.  It's fixed now and in proper form.  Sorry for any confusion. 


Interpreting what the 3rd and 4th rules mean properly, as well as linking up the contrapositive of the last rule to the not both part of the 3rd rule is the key to the game.

Rule 3:

Y  L or O

The Not both part of rule 3:

L & O  Y

link that with the first rule

L & O  Y  M

Rule 4:

L OR O     F & S

take the contrapositive of it:

F or S      L & O

Link that with the result from rule 3 and you get:

F or S    L & O Y   M

That chain takes out questions 10, 11 and 12 with ease and helps a lot on questions 8 and 9.

If you don't get that stuff together the game is a giant time trap that tries to burn you out while you write hypos all over the page and get really frustrated and feel like 

If you make rule 4  L AND O (instead of OR)    F & S the whole thing falls apart.

Hope this helps!
 
 

[Jack Daws]

Yeah, that makes sense and makes the game a lot easier 

I'm not understanding something tho. When you made the contrapositive of rule 4, how did you know to switch the "&" to "o"r and the "or" to "&"??

Does my question make sense? It looks strange when i write it out. 

[Dr. Troy]

Hey Jack,

Because a contrapositive essentially negates EVERYTHING as you make the sufficient condition(s) necessary and the necessary condition(s) sufficient (as you move the end-of-arrow items to the beginning of the arrow and vice versa), you must also negate any "and" or "or" language. So "and" (the combination of things) becomes "or" (individual things), and "or" (individual) becomes "and" (combined/group), and of course all of the variables or conditions themselves are also negated.

Consider this example:

"If Samuel attends the party, then Rachel and Ashley will also attend the party."

Diagrammed that would be: Samuel --> Rachel AND Ashley , meaning that Samuel's attendance indicates both Rachel and Ashley are also in attendance. So both girls going is necessary for Samuel to go.

To take the contrapositive, think about what would be sufficient/enough to know that Samuel did not go to the party. In this case, if either Rachel OR Ashley does not go to the party, then it must also be true that Samuel did not go (since both girls would have been there had Samuel attended).

Diagrammed: Not Rachel OR Not Ashley --> Not Samuel , meaning that the absence of even one of Rachel or Ashley tells you that Samuel did not go. This makes sense, as we knew that they both had to go for Samuel to go, so losing even a single piece of what was necessary tells us that the sufficient could not have happened (here, Samuel could not attend). And certainly if both Rachel and Ashley are both not in attendance then you would know that Samuel did not go either (all you need to meet the sufficient here is for either of the girls not to go, so you would definitely meet the sufficient here if both girls do not go).

Hope this helps!

[Ashley O]

Yeah, something screwed up with the BBC code and the strike through negatives didn't display.  It's fixed now and in proper form.  Sorry for any confusion. 

Oh, I get it now. The new diagram looks right to me now. 

[Jack Daws]

Hey Jack,

Because a contrapositive essentially negates EVERYTHING as you make the sufficient condition(s) necessary and the necessary condition(s) sufficient (as you move the end-of-arrow items to the beginning of the arrow and vice versa), you must also negate any "and" or "or" language. So "and" (the combination of things) becomes "or" (individual things), and "or" (individual) becomes "and" (combined/group), and of course all of the variables or conditions themselves are also negated.

Consider this example:

"If Samuel attends the party, then Rachel and Ashley will also attend the party."

Diagrammed that would be: Samuel --> Rachel AND Ashley , meaning that Samuel's attendance indicates both Rachel and Ashley are also in attendance. So both girls going is necessary for Samuel to go.

To take the contrapositive, think about what would be sufficient/enough to know that Samuel did not go to the party. In this case, if either Rachel OR Ashley does not go to the party, then it must also be true that Samuel did not go (since both girls would have been there had Samuel attended).

Diagrammed: Not Rachel OR Not Ashley --> Not Samuel , meaning that the absence of even one of Rachel or Ashley tells you that Samuel did not go. This makes sense, as we knew that they both had to go for Samuel to go, so losing even a single piece of what was necessary tells us that the sufficient could not have happened (here, Samuel could not attend). And certainly if both Rachel and Ashley are both not in attendance then you would know that Samuel did not go either (all you need to meet the sufficient here is for either of the girls not to go, so you would definitely meet the sufficient here if both girls do not go).

Hope this helps!

So the rule is that it ALWAYS changes then, right? AND always becomes OR, and OR always becomes AND.

Am I right?

[Jeffort]

Hey Jack,

Because a contrapositive essentially negates EVERYTHING as you make the sufficient condition(s) necessary and the necessary condition(s) sufficient (as you move the end-of-arrow items to the beginning of the arrow and vice versa), you must also negate any "and" or "or" language. So "and" (the combination of things) becomes "or" (individual things), and "or" (individual) becomes "and" (combined/group), and of course all of the variables or conditions themselves are also negated.

Consider this example:

"If Samuel attends the party, then Rachel and Ashley will also attend the party."

Diagrammed that would be: Samuel --> Rachel AND Ashley , meaning that Samuel's attendance indicates both Rachel and Ashley are also in attendance. So both girls going is necessary for Samuel to go.

To take the contrapositive, think about what would be sufficient/enough to know that Samuel did not go to the party. In this case, if either Rachel OR Ashley does not go to the party, then it must also be true that Samuel did not go (since both girls would have been there had Samuel attended).

Diagrammed: Not Rachel OR Not Ashley --> Not Samuel , meaning that the absence of even one of Rachel or Ashley tells you that Samuel did not go. This makes sense, as we knew that they both had to go for Samuel to go, so losing even a single piece of what was necessary tells us that the sufficient could not have happened (here, Samuel could not attend). And certainly if both Rachel and Ashley are both not in attendance then you would know that Samuel did not go either (all you need to meet the sufficient here is for either of the girls not to go, so you would definitely meet the sufficient here if both girls do not go).

Hope this helps!

So the rule is that it ALWAYS changes then, right? AND always becomes OR, and OR always becomes AND.

Am I right?

Yep, you've got it.  It's very formulaic and very easy to remember.  When taking the contrapositive of a conditional statement you simply reverse and negate everything. 

What is on the right of the  moves onto the left and vice versa.  Things in the negative in the original conditional statement get converted into the positive form and things that were originally in the positive form end up in the negative form in the contrapositive.  While doing that with compound conditional statements that include an AND or an OR and multiple variables on either or both sides of the conditional diagram, it's easy to remember.  AND (&) becomes OR and OR becomes AND (&).

To see the importance of this concept and practice it with a difficult logic game that is on point, check out the second game from PrepTest 31 June 2000, the one about CD's on sale.  It directly tests you specifically and heavily about it. 

[Jack Daws]

Ok, that makes sense. I'll make a note of that in the big notebook I'm keeping with LSAT stuff.

Are there any other terms or rules like that that appear in these sentences that I should know about?

[Trainwreck]

Ok, that makes sense. I'll make a note of that in the big notebook I'm keeping with LSAT stuff.

Are there any other terms or rules like that that appear in these sentences that I should know about?

I know that when "either/or" comes up, the negative is "neither/nor"

[LSAT Eliminator]

It's about logical opposites and negating statements. Virtually anything can be a condition (for example, this sentence has two very specific conditions: "if the bank is robbed by three women, then exactly one policeman is on duty"), but there are standard phrases that the test designers rely upon. "And" and "or" are great examples of those, and once you understand how they work, you can move through questions more quickly (and it really helps in Games!). You also see a lot of standard indicators such as "always" and "must" that have easy negations ("not always" and "not necessarily").

The key is to think about what an opposite is, and then imprint that so that during the test you don't have to stop and think about it. Most opposites come down to specifying something different than the condition. For example, in the example sentence above, the conditions are so specific that anything other than the condition (within reason) will be opposite. "Exactly one policeman," when negated could be "no policeman" or "two policemen" or whatever. So, the negation is really "anything but exactly one policeman" or "not exactly one policeman" Same for the "robbed by three women" condition.

[youknowryan]

Question aout the ~y -> L/O rule. I get that the most obvious contrapositive is L + O -> Y. But is not ~ L & ~O -> Y valid? I ask because most rules only diagram 2 ways and this one does 3. So if I were doing a game under time conditions and came up with the ~ L & ~O -> Y contrapositive, but not the L + O -> Y, it would make it impossible for get a clean chain.

Here's what I mean using L + O -> Y:

M -> ~Y -> L/O -> F+S

~F/~S -> L + O -> Y ->~M

I did not forget the F -> ~P and P -> ~F rule, it just is hard to get into this diagram since drawing diagonals is impossible.

Now if I found only ~ L & ~O -> Y, then there is no way to make a clean chain.

My question: how do I avoid such a circumstance?

[Jeffort]

Avoiding getting stuck in such a situation requires you to recognize the 3rd representation of the rule that is established by the phrase 'not both' regarding the L/O either or condition.  Unless otherwise specified, either/or situations on the LSAT are treated as inclusive, meaning that you are required to have at least one of the two, and are also allowed to have both.  In this game the 'not both' establishes an exclusive either/or situation, which means that selecting both renders a situation where the 3rd rule would be violated if you don't also select Y.  

It's really about thinking through all the parameters of each rule to make sure you understand its full repercussions when put into context with the other rules.  And yeah, if you fail to come up with L & O   Y from the rule, you cannot put together a nice clean chain with all the rules put together, which turns out to be the main key to this game.  One way to avoid getting burned by this same type of situation is to simply remember this game and how the 'not both' relating to compound necessary conditions generates the 3rd diagrammatic representation in case you encounter another game with the same rule construction so you'll see it and think " I've seen this before and know how it works, cool, let's knock out those questions."