Grouping Super Drill of Virtual Course, p 6-66

[rachue]

Hi, I don't understand why in question 6 of the grouping super drill that G can't be a correct answer. Nothing happens when G is chosen, which means it doesn't violate the last rule, so I don't see why it can't be with D. Thanks.

[Dave Killoran]

Did you get a chance to read the explanation of the drill in the answer key? It's fairly extensive, and the introductory portion specifically discusses the complex interaction of the second rule and the last rule, and understanding that interaction is essential to correctly answering question #6.

In short, even though G is a random, if you attempted to select just D and G, then none of the other variables would occur. But, take a look at the second rule—when B doesn't occur, either H or I occurs. Thus, you cannot have just D and G occur.

Remember, in grouping, it's not just the variables that are selected that can make things happen, but the unselected variables can also have an impact. If a rule contains a negative sufficient condition (as is the case in the second rule), when that condition is met (in this case, B is not selected)then something else must occur (H or I occur).

Take a look at that explanation and please let me know if that makes sense. Thanks!

[rachue]

Hey, I do remember reading that but I guess it just didn't click at that time. Thanks for the clarification!

[Dave Killoran]

Always check those explanations twice! Usually when there is a tricky point like this one, we explain it

Thanks!

[Mike P.]

I'm also stuck on question #6.

Why can D not appear with C? Am I missing a rule or an inference here? If C occurs, what else must occur?

[Adam Tyson]

It's the same reason that D cannot occur with G, as described earlier in this thread, Mike. It's not about D and C having a problem with each other; it's about that crucial rule about B.

If D occurs, then only one other thing occurs. If that one other thing is C, then B does not occur. But if B does not occur, you need H or I to occur, and now D is with more than one other thing!

For more about that rule and others like it, you might want to check out this article from the Powerscore LSAT Blog:

https://blog.powerscore.com/lsat/the-mo ... rule-lsat/