A logic question

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• 1 Like

  10000019 Alum Member

  August 2017 edited August 2017 3279 karma

  Disclaimer: I'm a newb, so you'll probably want to wait for someone more experienced to reply.

  Are you using the + to indicate 'or' xor 'and'?
  I'm replying with the assumption of 'or'.

  I do not think it is logically valid to draw that conclusion, because you leave open the possibility of A=0, C=1, B=1.

  If they are saying A=1, C=1/0, then B=1, that is logically valid.
• 1 Like

  Seeking Perfection Alum Member

  August 2017 edited August 2017 4423 karma

  The above comment is right if + symbolizes or, but in my experience + is usually used to mean and. If that is the case, it is valid. If A implies B. Then A and C will always imply B. This is because A and C implies A and A implies B.

  A-- >B
  A and C
  A (If you have both A and C you definitely have A)

  ---

  B (A implies B and you have A so you have B )

  P.S. I found that using the word implies in place of the conditional arrow clarifies things for me. Some people just say arrow or say A-->B as "If A then B." But I think it's important to have some way of thinking it as a word or group of words which expresses the meaning.
• Seeking Perfection Alum Member

  August 2017 edited August 2017 4423 karma

  Edit: Posted explanation of spelling mistake in previous comment, but then remembered I could edit it.
• The Noodley Alum Member

  August 2017 662 karma

  @10000019 Sorry I was not very precise in my diagram. I meant an "and".
• The Noodley Alum Member

  August 2017 662 karma

  @"Seeking Perfection" Thanks for the explanation! I did not think that "A and C" can always imply A, so the original conditional relationship can still work!
• 1 Like

  Will Dearborn Alum Member

  August 2017 edited August 2017 218 karma

  If it's A AND B then you know that BOTH A and B together are sufficient to trigger the necessary condition. On the other hand, if it's A OR B, then either A or B or both are sufficient to trigger the necessary condition. In that specific question, we get one condition that is sufficient for us to trigger the necessary condition. The premise states A-->B so it doesn't really matter in this specific instance, if we get A, B, C, D together. As long as we get A, we know that B must occur.
• The Noodley Alum Member

  August 2017 662 karma

  @Patroclus got it! thanks for the explanation!