Questions for diagramming

[rdee81]

I have purchased the 2020 2021 LSAT Logic Games Bible, and I have written questions. I listen to the podcast on You Tube and what really inspired me is when Dave and Jon said that Im not alone. They said, its someone out there with the same questions and struggles. Therefore, Im putting myself out there to find answers to what questions linger in my mind or what's left of it.

Page 6/ Question #1: Why isnt the answer A? I thought the double arrow meant if and only if. Also, what symbol can I use to mean the word unless? Lastly, In answer E why is the J crossed out if Jin is selected.

Page 7/ Question #6 The answer is B. Why is it B because to me A can represent the diagram too? I used the process of elimination and I chose A or B, but why is it B? Do you go by the letter in the middle?

Page 12/ Question #6 Wh do you need the contrapositive in this question?

I have many more questions, but I wont ask an enormous amount of questions this time anyway.

[Adam Tyson]

Hi rdee81, happy to help you with these!

The diagram on page 6, question 1, is J W. This can be interpreted as "if J is selected, then W must be selected." This is not a double arrow "if and only if" relationship. W, the Necessary Condition, can be selected even if J is not. But the contrapositive of that relationship, where we reverse the order and negate the terms, would be "if W is not selected, then J cannot be selected," and that is answer D. Answer A also isn't a double arrow; it's saying that if J is NOT selected then W must be, or J W. Not the same as our original diagram! That answer is describing a situation where at least one of J or W must be selected, and possibly both. If one is out, the other must be in, so at least one must be in. Oh, and "unless" is a Necessary Condition indicator, so whatever the word Unless refers to, just put that on the right side of the arrow! The other thing must be negated to form the Sufficient Condition - we call that the Unless Equation, and you can read more about it in the Logical Reasoning Bible.

For question 6 on the next page, the diagram put N in between M and O, with either order being possible. That makes N the key variable in that rule, and it means that N must be after one and before the other. N cannot be before both, nor can it be after both. Answer A, on the other hand, only deals with the relationship between M and N and says nothing about O, so it doesn't leave us with just those two sequences. For example, a sequence of M-O-N would satisfy answer A, but would conflict with the diagrams we were given! The correct answer has to deal with all three of those variables, and it must ensure that N is always between the other two no matter which order they are in.

For page 12, question 6, it's not about whether we need the contrapositive, but about understanding exactly what the contrapositive would be. In a two-value system, where every variable is in exactly one of two possible positions, saying that a variable is not in one of those positions is the same as saying that it is in the other position. Using that positive approach - showing where it is, rather than where it isn't - can be very helpful, because it's often easier to think of the positives than the negatives. It's also the sort of this you are likely to be asked about! Adding this layer of thinking to your process will allow you to more quickly and easily spot key inferences. You don't have to do it, but you'll be better off if you do!

I hope that helps. Feel free to ask more!