IDEAS: Negated double sufficient condition and double NC...

youknowryan
Posts: 182
Joined: Mon Aug 18, 2008 3:20 am

IDEAS: Negated double sufficient condition and double NC...

Postby youknowryan » Thu Jun 30, 2011 3:12 pm

If it is not the case that the zoo contains both bears and yaks, then it contains lions and zebras.

Is this the right diagram?

~B & ~Y -> L & Z

~L or ~Z -> B or Y

I know this looks like the SuperPrep B rule, but in this case I am asking about this rule as it stands.
Last edited by youknowryan on Thu Jun 30, 2011 3:48 pm, edited 2 times in total.

Asleep
Posts: 89
Joined: Thu Jan 06, 2011 2:29 am

Re: IDEAS: Negated double sufficient condition and double NC...

Postby Asleep » Thu Jun 30, 2011 3:22 pm

Not quite. If there are either bears and no yaks or yaks and no bears, then lions and tigers still must be present. It should be written as this:

~(B and Y) -> L and Z

This is equivalent to :
~B or ~Y -> L and Z
-------------------------------------------
The contrapositive is:
~(L and Z) -> ~~ (B and Y)

This is equivalent to:
~L or ~Z -> B and Y

Hope this helps!

User avatar
suspicious android
Posts: 938
Joined: Tue Feb 09, 2010 4:54 pm

Re: IDEAS: Negated double sufficient condition and double NC...

Postby suspicious android » Thu Jun 30, 2011 10:05 pm

We just did a whole long thread about this rule like a week ago, coincidentally.




Return to “LSAT Prep and Discussion Forum”

Who is online

Users browsing this forum: Instrumental, njames1961, Veil of Ignorance and 7 guests