#3 - Local, Must Be True

[Dave Killoran]

Complete Question Explanation
(The complete setup for this game can be found here: lsat/viewtopic.php?t=15710)

The correct answer choice is (A)

If L is added last, from our first inference we know that Z cannot be added first. Thus, as stated in answer choice (A), at least one of the foods is added at some time before Z.

[ccude9]

The rules state that if the zucchini is added first, then the lentils are added sometime before the onions.

In the correct answer, if the lentils are added last then: A. At least one of the foods is added at some time before the zucchini.

I believe the conditions in the rules are as follows:
Sufficient: If the zucchini is added first
Necessary: Then the lentils are added sometime before the onions

In the question, if the lentils are added last, shouldn't this suggest that " at least one of the foods is added at some time before zucchini" could occur but not MUST occur?

Does the necessary condition in the question override the necessary condition in the rules?

Thank you!

[Dave Killoran]

Hi C,

Let's start with the rule, and then look at the question itself.

You've got the rule correct here:


Z1 L > O


So, when the question stem adds in that "the lentils are added last," what do we then know? We know that L > O cannot occur. Thus, the necessary condition above cannot occur, enacting a contrapositive:


L > O (or, O > L) Z1


Consequently, Z cannot be first, and as you note, "At least one of the foods is added at some time before the zucchini." (A) is therefore correct.

Based on your analysis, you understood everything, so I'm thinking maybe you mis-read the answer key here?

Please let me know. Thanks!

[myverdict]

Why can't the answer be C - The mushrooms are added third?

The first rule says if mushrooms are added third, then the lentils are added last.

M3 ------> L6

Does this mean that if L6 is there then it's not necessary for M3 to be there? Please confirm.

[Ladan Soleimani]

Hi myverdict,

Your last sentence is correct. Knowing that the lentils are added last means that it is possible for the mushrooms to be third, but it is not necessary. The only things you can know for certain with this rule are that if the mushrooms are added third, then the lentils must be added last and the contrapositive of the rule: if the lentils are not added last, then the mushrooms cannot be added third.

Hope that helps!
Ladan

[vsumpter]

For this question I became sooo confused. Based not the rules it states that if mushrooms are added third then the lentils are added last. So why in this answer choice is (c) not the correct answer.

Nevermind, after completing more of the online homework it now makes sense that this specific question is to confuse me into "Mistaken Reversal." I will keep the question up just in case anyone has further questions but I suggest they look at the explanations for Avoiding False Inferences explanations VERY HELPFUL!!

[James Finch]

Hi vsumpter,

Just to further explain this particular question for anyone else who might run into a similar issue, the first two rules give us two conditional statements that can be combined into an A C chain. We have:

Rule 1) M3 L6, and its contrapositive L6 M3

Rule 2) Z1 L--O, and its contrapositive O--L Z1

By combining these two rules, we can create two chains that will allow us to answer some of the questions, including question 3:

M3 L6 O--L Z1

and

Z1 L--O L6 M3

For this question, we're given L6, from which we can infer O--L Z1, or in plain English, that Z can't go in the first slot. However, as vsumpter noted, we can't infer anything about M, as that would be an invalid Mistaken Reversal.

Hope this helps!

[Katya W]

Hi, my question is, if you didn’t infer the link between the conditional statements, how else can you solve this problem? I was able to get the right answer but it took me forever because I had to create skeleton diagrams and use the process of elimination. Thank you!

[Paul Marsh]

Hi Katya! This problem becomes much more time consuming if you haven't made the inference that the first two rules play into each other. The solution is not to look for alternate ways of solving this problem, but to instead strengthen your inference-making skills. After you finish writing down all the rules but before moving onto the questions, make sure you take a substantial amount of time to look over all your rules and see if there's any way those rules can be joined together to make inferences. The simplest way to do this is to look for any variables that appear in more than one rule. In this game, L appears in both Rule 1 and Rule 2. That gives us a strong indication that those rules can work together somehow. Even if you can't figure out how to chain together the conditionals, think through it one step at a time. "Ok, if L is 6th, what does that mean for the O-L order? And how would that affect Z?" While practicing Logic Games initially, take more time than you think is necessary to look through all the rules and see which variables appear more than once. (Of course, there are other inferences that come from more than just a variable popping up twice in the rules. But that's a great place to start!)

If conditionals are proving difficult for you, go back and review all the practice problems in the PowerScore Bibles and Course Books dealing with them. Work on taking contrapositives and chaining conditionals together. Conditionals are an area that many people struggle with initially while studying for the LSAT, but mastering them is really important for getting a high LSAT score.

Hope that helps!

[Katya W]

Hi Katya! This problem becomes much more time consuming if you haven't made the inference that the first two rules play into each other. The solution is not to look for alternate ways of solving this problem, but to instead strengthen your inference-making skills. After you finish writing down all the rules but before moving onto the questions, make sure you take a substantial amount of time to look over all your rules and see if there's any way those rules can be joined together to make inferences. The simplest way to do this is to look for any variables that appear in more than one rule. In this game, L appears in both Rule 1 and Rule 2. That gives us a strong indication that those rules can work together somehow. Even if you can't figure out how to chain together the conditionals, think through it one step at a time. "Ok, if L is 6th, what does that mean for the O-L order? And how would that affect Z?" While practicing Logic Games initially, take more time than you think is necessary to look through all the rules and see which variables appear more than once. (Of course, there are other inferences that come from more than just a variable popping up twice in the rules. But that's a great place to start!)

If conditionals are proving difficult for you, go back and review all the practice problems in the PowerScore Bibles and Course Books dealing with them. Work on taking contrapositives and chaining conditionals together. Conditionals are an area that many people struggle with initially while studying for the LSAT, but mastering them is really important for getting a high LSAT score.

Hope that helps!

Thank you Paul! I appreciate your thorough response here and on my other post! I have been trying to make as many inferences as I can since then.

Also, I just noticed this, and I can’t remember if I read it in the Bibles anywhere, but the connections between the two rules are made by connecting one rule with the contrapositive of the other rule. This is allowed? When I think about it, it seems to go against the logic to connect one rule’s contrapositive with another rule’s non-contrapositive. Thank you!!