Need Help Memorizing Contrapositives!

stupidcha
Posts: 3
Joined: Sun Jan 02, 2011 7:36 pm

Need Help Memorizing Contrapositives!

Postby stupidcha » Mon Aug 08, 2011 6:41 pm

My brain is going mush from all the studying. This is what I did in a problem moments ago. Pg 208 in LGB

K -> X
then
X -> K

This is wrong I believe. I don't know why though...

So if ~X, then ~K?

Thus B? answer turns out to be A and I understand the reasoning behind it but my brain seems to like to do the problem like the way shown above.

Does anyone have an easy way to remember these contrapositives? Seems like they aren't really sticking with me.
Thank you!

User avatar
Ruxin1
Posts: 1284
Joined: Fri Jul 23, 2010 3:12 pm

Re: Need Help Memorizing Contrapositives!

Postby Ruxin1 » Mon Aug 08, 2011 6:42 pm

stupidcha wrote:My brain is going mush from all the studying. This is what I did in a problem moments ago. Pg 208 in LGB

K -> X
then
X -> K

This is wrong I believe. I don't know why though...

So if ~X, then ~K?

Thus B? answer turns out to be A and I understand the reasoning behind it but my brain seems to like to do the problem like the way shown above.

Does anyone have an easy way to remember these contrapositives? Seems like they aren't really sticking with me.
Thank you!


Image

stupidcha
Posts: 3
Joined: Sun Jan 02, 2011 7:36 pm

Re: Need Help Memorizing Contrapositives!

Postby stupidcha » Mon Aug 08, 2011 6:51 pm

wait what? flame? hmm...

User avatar
minnbills
Posts: 3153
Joined: Thu Sep 02, 2010 2:04 pm

Re: Need Help Memorizing Contrapositives!

Postby minnbills » Mon Aug 08, 2011 6:54 pm

Well flame or not here you go:

Just flip and negate.

If A, then B

becomes

If not B, then not A

cking2014
Posts: 16
Joined: Sun Jul 10, 2011 12:34 am

Re: Need Help Memorizing Contrapositives!

Postby cking2014 » Wed Aug 10, 2011 8:57 pm

A -> B

contrapositive:

~B -> ~A

just flip and negate each side, best way to remember!!




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