PT63.S1.Q21 - on the discount phoneline

mitrakhanom1

I'm confused when, where and how the word "not" is used sometimes. For example, in this question answer choice E's conclusion is translated to if a university class is not conducted in a normal classroom, then it will be conducted in a laboratory. /UC ---> L
I thought "not" is group four and negates the necessary condition? Is it because the if already designates the sufficient condition and therefore the not stays on the sufficient as opposed to moving to the necessary side?
http://7sage.com/lsat_explanations/lsat-63-section-1-question-21/

nye8870

"Not" isn't in group 4. "Not both" is but rather than a negation it means (either)A .. (or)B ...or (neither). "Not" cuts the world into two halves. Either something "is" or it is "not". In a stimulus, when you are writing out the lawgic, "not" is like an attribution of a characteristic. In lawgic, as you have demonstrated, we use a (/) symbol aside a variable to indicate that whatever the variable stands for...it's not the case or it doesn't happen.
I found watching the video lessons in this area over and over very helpful

nye8870

Incidentally, in this PMR question we are looking at a bi-conditional. So either A is the case or B is the case and A&B cannot occur simultaneously. Either a call is placed between 9-5 or a call is placed sometime outside those hours. These are the only two options. Same thing happens in ac(E)...either class is conducted in a lab or a normal classroom. There are no other options and a class is never conducted in both.