Sufficient & Necessary Practice II

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It’s all in the title. We will give you the tools, but you are the one who has to use them on LSAT questions. And, it’s not just enough for you to use them, but you need to weather them. Use them enough to blunt them, crack them, break them until you are the tool. Getting metaphysical enough for you? What is Naz trying to say today? Practice, people! Practice! Let’s begin some sufficient and necessary practice right now!

1. All cats sleep in the morning

C ===> SM

not SM ===> not C

Here we have our basic sufficient and necessary statement. If it is a cat, then it is asleep in the morning. Easy.

2. No cat is a dog.

C ===> not D

D ===> not C

Again, let’s look at the necessary situation here and make sure it works. Can it be true that something is neither a cat nor a dog? Of course. How about a frog!

3. If Peter is not an electrician, then he must be an architect.

not E ===> A

not A ===> E

Here we have an example of our classic either/or sentence. Can it be true that someone is both an electrician and an architect? Yes it is.

4. Sarah can pass the exam only if she studies this evening.

P ===> SE

not SE ===> not P

Here we see our “only if” rule in action. Put an arrow through the “only if” and then whatever is to the left of the “only if” is the sufficient condition and whatever is to the right of it is the necessary condition.

5. Joanne will not attend prom unless Nancy also attends prom.

Jp ===> Np

not Np ===> not Jp

Here we see our “unless” rule in play. You place the arrow through the “unless” and negate whatever is to the left of it. Therefore, Joanne will not attend prom becomes Joanne will attend prom.

Alright, so now you have to do the rest. Now get back to your LSAT prep and practice, practice, practice!

Happy Studying!

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Updated on Aug 18, 2016