#8 - Local, Could be True

[Dave Killoran]

Complete Question Explanation
(The complete setup for this game can be found here: lsat/viewtopic.php?t=11091)

The correct answer choice is (C)

The condition in the question stem produces the following setup:

December 97_game#2_M12_L3_explanations_game#4_8_diagram_1.png

As shown by the diagram above, L could perform fourth, and hence answer choice (C) is correct. In considering this answer choice, some students eliminate it because they make a Mistaken Reversal of the third rule. Just because N performs fifth does not mean that L performs third, and so answer choice (C) cannot be eliminated on the basis of the third rule.

[ccude9]

The question asks if Norton is schedule 5th, which of the following could be true?

The correct answer is C: Lalitha is scheduled for the 4th performance...

However, one of the rules states that Lalitha performs 3rd only if Norton performs 5th

In this questions, Norton does indeed perform 5th, therefore, wouldn't Lalitha have to perform 3rd?

HELLPPPPPP

[Dave Killoran]

Hi C,

No problem--you are making a Mistaken Reversal of the rule, and that is causing the issue. Let's look at it a bit more closely, and see what is going on.

The rule in game reads:


L3 N5


So, if L is in 3, then N must be in 5. But, if N is in 5, does that mean that L must be in 3? No, and that's what is occurring here. When N is in 5, then L can be in 3, but L does not have to be in 3, and it could be in 4.

As you can see, this question is placed specifically to test your understanding of conditional reasoning. This is a pretty easy mistake to make, but hopefully now that you've seen it, you will be able to avoid it in the future

Please let me know if that helps. Thanks!

[ccude9]

Got it! Thanks for the help, Dave!

[alexmelendez28]

Hi,

I am still having a hard time understanding questions # 8 .. So IF Norton is scheduled for 5th performance, then Lalitha DOES NOT HAVE TO BE 3rd?? ..

why is this a mistaken reversal?

The rule says L performs 3rd ONLY IF" N performs 5th...he is scheduled to perform 5th..

I don't get it ..

sorry!!

[Dave Killoran]

Hi Alex,

No problem, let's see if we can clear this one up for you!

First, let's go back to the rule in the game, which can be diagrammed as:


L3 N5


Note the direction of the arrow--it goes from L3 over to N5. So, if L is in 3, then you know automatically that N is in 5. But, is the reverse true? No, it isn't, and that's the essence of a Mistaken Reversal. When N is in 5, then L could be in 3, but L doesn't have to be in 3. This results from the direction of the arrow.

Let's look at an example from a totally different arena. Let's say that I make the statement, "To get to the roof of the building, you must take the stairs." That would be diagrammed as:


Roof Stairs


so, according to that statement, if you are on the roof, then you took the stairs. But, let's just say that all I knew about you was that you were taking the stairs. Does that mean that you went to the roof? No, because you could have gone to the second floor, or the fourth floor, etc. In essence, what isn't known to be true is this statement:


Stairs Roof


That statements isn't true for sure, but thinking that it is true is what is known as a Mistaken Reversal.

Please let me know if that helps clear this up. And, if you have any of our materials (such as the LSAT Bibles), let me know which ones, and I can refer you to particular page numbers so you can read more about contrapositives, Mistaken Reversals, and Mistaken Negations. They are all elements that you want to be rock solid on as they frequently appear in LG and LR questions. Thanks!

[alexmelendez28]

Hi Dave!!!

Thank you so much!!

I think I got it...

when L is 3rd it is the sufficient condition and so therefore N5 becomes the necessary...according to the rule.

however, the contrapositive, would be written as N5 --> ~L3 ... because from what I have learned, the necessary does not mean that L3 must occor only that it can occur.

I guess the rule threw me off because it says "ONLY IF" ..

How was I suppose to know though that I had to write out the contrapositive to figure this out?

this was a tricky question..

Dave thanks

[alexmelendez28]

Hi Dave

Me again! just read pg 58 of the Logic Games Bible (SO AWESOME TO USE ALONG SIDE WITH THE WORK BOOKS FOR LIVE ONLINE) ..

It just mentioned that contrapositives are present in ALL conditional statements!!!

Now this all makes sense!!!

Let me know if I am on the right track with this

Thanks!!!

[Dave Killoran]

Hi Alex,

Glad I could help

Think about the contrapositive as a constantly present element whenever a conditional statement occurs. For example, if I know L3 N5 is true, then automatically I know that N5 L3 is also true. Over time, this becomes something you always know, not something you have to actively think about. Thus, as you move forward in your studies, you will find that thinking about contrapositives become second nature. At that point, you being to see all the possibilities both more quickly and more clearly, and you becomes a faster and stronger LSAT taker

Please let me know if that makes sense. Thanks!

[Adam Tyson]

Alex, remember that "Only If" indicates a necessary condition, unlike "If" all by itself which indicates a sufficient condition. "L is 3rd only if N is 5th" means that N5 is necessary whenever L3 happens, but N5 can happen even if L3 doesn't. The necessary condition is allowed to happen whether or not the sufficient happens, but when the sufficient happens the necessary MUST happen.

The contrapositive is when we both reverse the order of the terms AND negate those terms. Dave diagrammed that for us.

Most of my students who initially struggle with conditional reasoning eventually have a major breakthrough, when it all suddenly makes much more sense and they start doing it automatically and almost without thinking. You can get there, too!

Good luck!