Hi @arctan1, thanks for your post, but our review of the answer explanation indicates that it does match the question.
The problem sets out the following:
P: A ==> not C
P: B ==> C
P: ? [missing premise]
C: A ==> X
Answer (A) provides as the missing premise not X ==> B. This is correct, as follows:
P: A ==> not C
CP: C ==> not A
P: B ==> C
CP: not C ==> not B
P: not B ==> X
CP: not X ==> B
C: A ==> X
CP: not X ==> not A
Transitive A ==> not C ==> not B ==> X
CP of transitive: not X ==> B ==> C ==> not A
Hope this helps! Please let us know if you have any additional questions.
arctan1August 29, 2017
can't read your message but i imagine it was a thorough explanation
chamoritta112February 1, 2018
I don't understand how the variable D became a part of the premise when the initial problem set did not include variable D.
ninapogorzelskiApril 26, 2018
I do not understand either
arctan1June 3, 2018
dudes got a glitch in his bot lol
arctan1June 3, 2018
i like the way this app trains your brain and the way it approaches the LSAT material in general, very methodical.
MehranJune 5, 2018
@arctan1 are you still unable to see our response here?
arctan1July 19, 2018
yes I can see the response now
lizaclark95February 23, 2019
The actual explanation in the main screen is still wrong!
RaviFebruary 25, 2019
@lizaclark95,
Thank you for bringing this to our attention. I will alert the technical team about this.
For future reference, if you spot any glitches like this, feel free to also call our support team at 855.483.7862 ext. 2 Monday-Friday 9am-6pm PT. They can quickly relay problems to the tech team.
You're right—while the correct answer is listed, the explanation is incorrect. For your reference, I will walk through this question's correct explanation now.
P: A - >not C C - ->not A
P: B - >C not C - ->not B
P: ?
C: A - >X not X - >not A
We need to link the premises up to see how we can get to the conclusion and what might be missing. C is the common element in the two given premises, so let's link them up using C
A - >not C - >not B B - >C - >not A
The conclusion we're given is A - >X. X is missing from our premises, so clearly we need an X in the missing premise. How can we conclude that A - >not X?
What if we put and X at the end of our statement starting with A?
A - >not C - >not B - >X
In this chain, we've added not B - ->X as a premise, and with this additional premise, we can conclude that A - >X
Thus, we know that not B - >X is our answer. In the answer choices, the contrapositive of this (which is not X - >B) is given, so we know this is the correct answer.
Does this explanation make sense? Let us know if you have any more questions!
marthajanidsilvaSeptember 28, 2019
The explanation (premise 2) is written wrongly on the answer
LucasDecember 4, 2019
How do I figure out which one to pick. I knew that if x exists, then B could not be present. I'm always stuck guessing between then two. I figure out the logic part pretty easy, but could not figure out between A and B
LucasDecember 4, 2019
Also, where does D come from in the explanation
Latell19January 27, 2021
How do you know when you apply the contra positive. There are some questions like this but the outcome doesn't require you to find the contrapositive for the answer.
