Setup and Rule Diagrams

[Dave Killoran]

Hi Joy,

The diagram would be the same. The "or" inherently allows for both to occur, so they didn't really need to add the "or both." They probably did so because the prior rule contains a pairing where it is specified to be "both." They probably wanted to avoid any confusion there, and thus added "or both." but it's not necessary, and doesn't change the diagram at all.

Please let me know if that helps. Thanks!

[jling]

Yes it helps! Is it safe to say that the wording "or" will imply "both" when I see it in conditional types of questions?

Thanks,
joy

[Dave Killoran]

Yes, it always does! The exceptions are when the terms cannot occur together by definition (such as day and night, rich and poor, etc) or when there are outside restrictions that would disallow both being selected together (such as a rule that limits total numbers selected, or if "but not both" was added, and so on).

Thanks!

[jling]

Thanks! It's super helpful.

[LSAT2018]

For the last rule If the stand carries watermelons, then it carries figs or tangerines or both I would just like to clarify a few things about the contrapositive.

Watermelons → Figs or Tangerines
Watermelons → Figs and Tangerines

Not Figs and Tangerines → Not Watermelons
Not Figs or Tangerines → Not Watermelons

Would I have to consider the contrapositive for the case that the fruit stand carries both figs and tangerines?

[kimber1492]

I am confused. Why can't you use the double not arrow for T & K as well?

[James Finch]

Hi LSAT 2018 and Kimber,

LSAT 2018--The LSAT uses "or" to be inclusive of the possibility of both necessary conditions potentially occurring, with only one definitely occurring. So the correct way to diagram the last rule would be:

W F or T

with the contrapositive:

F and T W

So we would need to to know that neither F nor T were included to correctly infer that W is not included either; both have to be out for us to know W is out.

Kimber-- T and K are dealing with the somewhat counter-intuitive rule that at least one of them must be included, ergo:

T K,

and

K T

This means that at least one of K or T must be included, but the possibility also exists for both to be in. We just can't have both out.

Hope this clears things up!

[smilit1]

I get the: not T not K. Therefore, at least one or both must be IN.
However, wouldn't it also be correct to say: K P. Therefore, at least one or both must be OUT?

[Adam Tyson]

That is correct! If K is in, P is out, and if P is in, K is out, so there is that double-not-arrow relationship between K and P. Well done!