"Either write something worth reading or do something worth writing."– Benjamin Franklin

Mehran August 30, 2016

@scdinkel21 (A) and (C) are very different.

(A) says if you write something worth reading, then don't do something worth writing.

(C) says if you don't write something worth reading, then do something worth writing.

Remember to diagram "either/or," pick a variable and negate it for your sufficient condition. The other variable is your necessary condition.

Hope this helps! Make sure you watch our video lesson on Sufficient & Necessary conditions for a more in-depth discussion of these concepts.

loreleehappyangel February 15, 2018

How do you decide which one has the be the necessary condition?

Mehran February 27, 2018

Let's try an example:

Either X or Y

It doesn't matter which variable you choose, but you will pick one and negate it and that will be your sufficient condition. The other variable will be the necessary condition.

So let's pick X:

Not X ==> Y

Now imagine you picked Y instead of X so your diagram would be:

Not Y ==> X

Which is the contrapositive so these statements are identical in meaning:

Not X ==> Y
Not Y ==> X

That is why it doesn't matter. When you write the contrapositive, you will have both possibilities.

Hope that helps! Please let us know if you have any other questions.