or

Lsatbreakingnews

How is the group 3 or inclusive?? Doesn't negating one element make it exclusive?

For example Jon or Tommy will go to lunch is translated as:
/J -> T
/T -> J

Doesn't that make it so we can only choose one at the expense of the other making it exclusive?

Accounts Playable

No. Think of it like this:

Not J-->T

What can happen?

J is in. J is out. T is in. T is out.

If J is in, the rule is irrelevant. T can float in or out, which makes this "or" statement inclusive since it's OK for T to still be in.

If J is out, we know T must be in (since this is an "or" after all).

If T is in. The rule is irrelevant. J can float in or out; again, making this option for J an inclusive "or."

Finally, if T is out, J must be in.

Lsatbreakingnews

Thanks that was a clear explanation. I see how it makes it that at least one of the elements must be in.

draj0623

Just to add to the very thorough response of @"Accounts Playable", "Or" just precludes the world where both J and T are both out, since you must have one or the other or both. This was very hard for me to understand initially and reviewing the core curriculum lesson on "or" and "not both" really helped me make my way towards understanding.

Lsatbreakingnews

Thanks draj:)