If Veena volunteers, then which one of the following could be true?

jskaggs on April 2, 2019

Question about in/out of variables

In the video explanation it says that since V is in it satisfies the rule that V or S must be in. However, the answer for this question is that F and S could volunteer as well. I understand how F could be a possibility, but how is S? You can have both V and S in at the same time? I Thought if one was in the other was out. Am I wrong in this? You can have both letters in at the same time? Likewise, you can have L and R in at the same time? (rule 4)

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Jacob-R on April 3, 2019

I’m happy to help. Understanding the direction of the condition is absolutely crucial, for this and for many other LR and LG questions. The rule in question states:

If no S -> V.

The contrapositive of this rule is:
If no V -> S.

Notice that this is NOT the same thing as saying that if V is IN, then S is OUT. The direction is crucial! Both the rule and the contrapositive only tell us something about the situation in which either S is OUT or V is OUT.

Therefore, in question 2, when we are told that V is in, the rule referenced above does not get activated! And that is because the direction of our conditional statement always starts with either S or V not being in.

Same exact thing for rule 4.

If no R -> L.

If no L -> R.

Does that help? Let us know if this concept is not clicking, because it is absolutely crucial!