Logic Games Bible P. 223 Game 1 October 1996 #6 Forum

[legalized]

WHY is the answer A? Their explanation didn't clear that up for me.

I did mess this up by originally starting to set up by filling in all the L/M/R pair possibilities, then thought I was wasting time I could use to solve only given hypotheticals and went ahead to answering the questions. All the answers for every question were given in alphabetical order of the letters representing areas to be reduced, and silly as this sounds having began my setup with the LR or LM, I ended up filling in blanks "out of order" and it seems to have messed me up to not be in the same order as the answers. I made a note to myself to do grouping in alphabetical order.

Anyway, why is the answer A when G and W are played and W isn't suppose to be possible if both G AND S aren't played?

The way I have that rule written (and it's inverse) is:

W ---> G + S (read "W is reduced if G AND S are reduced"); [strike]G[/strike] OR [strike]S[/strike] ---> [strike]W[/strike] (read "if G is not reduced OR S is not reduced, then W is not reduced")

So where did I go wrong on #6?

Thanks in advance.

[Cambridge LSAT]

You've reversed the orders of both the rule and its contrapositive. Here's how they should look:
G and S → W (rule)
[strike]W[/strike] → [strike]G[/strike] or [strike]S[/strike] (contrapositive)

Since "if" precedes G and S in the original rule, this part of the statement is the sufficient condition.

W ---> G + S (read "W is reduced if G AND S are reduced")

The way you've diagrammed this with the arrow actually reads "If W is reduced, then both G and S are reduced."

In choice A of question #6, the presence of W does not trigger the first rule. W is the necessary condition. The rule is only triggered by the presence of both G and S (the sufficient condition), or by the lack of W (the sufficient condition of the contrapositive).

[legalized]

You've reversed the orders of both the rule and its contrapositive. Here's how they should look:
G and S → W (rule)
[strike]W[/strike] → [strike]G[/strike] or [strike]S[/strike] (contrapositive)

Since "if" precedes G and S in the original rule, this part of the statement is the sufficient condition.

W ---> G + S (read "W is reduced if G AND S are reduced")

The way you've diagrammed this with the arrow actually reads "If W is reduced, then both G and S are reduced."

In choice A of question #6, the presence of W does not trigger the first rule. W is the necessary condition. The rule is only triggered by the presence of both G and S (the sufficient condition), or by the lack of W (the sufficient condition of the contrapositive).

Crap. Thanks. I usually can pick up on my mistaken reversals immediately on review (and hardly make any, actually)...this one got me good!