Please help me with sufficient assumption and necessary assumption questions

Comments

• rader.thomasp Member

  January 2018 4 karma

  I could be wrong as I am only a couple months into this as well, but I think the underlying lawgic can be the same, as you suggested above, but the questions diverge when translated into english. Read this lesson on Necessary Assumptions:
  https://7sage.com/approach-necessary-assumption-questions/
• Sami Yearly + Live Member Sage ⭐ 7Sage Tutor

  January 2018 10806 karma

  @sjkimkim said:
  I went through JY's courses and have a question I just can't seem to solve by myself.

  JY explained that sufficient assumption questions are something like:
  Premise: A
  Conclusion: B
  Answer: A->B

  But I keep thinking that this type of question could also be a necessary assumption question.
  Obviously, A->B is necessary to get to the conclusion B.

  So, my question is, are these "fill the gap" kind of questions both sufficient assumption and necessary assumption questions at the same time??

  Great question! I remember it was a big hurdle to overcome when I was first starting out with NA questions because A-->B is so strong for an NA answer choice.

  In this case A-->B is both necessary and sufficient. Because if there was even one instance where A was present but not B or we knew B was not present but A was, we could no longer conclude that if we have A, we can conclude B.
• Alex Alum Member ⭐

  January 2018 edited January 2018 23929 karma

  As always, @sami nailed it better than I ever could. One thing I wanted to add is to make sure you really understand the ideas of what it means to be sufficient and what it means to be necessary. Not just the theory behind those words but what it looks like in actual practice on questions.

  For instance, if I tell you I want to buy a pair for shoes from the store that cost $80, is it sufficient or necessary that I have $80 in my pocket at the store?

  What if I have $90?

  What if I have $10?
• 1 Like

  LCMama2017 Alum Member

  January 2018 2134 karma

  @"Alex Divine" said:
  As always, @sami nailed it better than I ever could. One thing I wanted to add is to make sure you really understand the ideas of what it means to be sufficient and what it means to be necessary. Not just the theory behind those words but what it looks like in actual practice on questions.

  For instance, if I tell you I want to buy a pair for shoes from the store that cost $80, is it sufficient or necessary that I have $80 in my pocket at the store?

  What if I have $90?

  What if I have $10?

  Can I answer? I say for the first Q - if you have $80 and the shoes cost $80 then it is sufficient that you have the $80 to pay for the shoes
  For Q2 - it is sufficient to have the $90 to buy the shoes
  For Q3 - you only have $10 so it is necessary to have $70 to buy the shoes

  Did I pass?
• Sami Yearly + Live Member Sage ⭐ 7Sage Tutor

  January 2018 10806 karma

  @LCMama2017 said:
  Can I answer? I say for the first Q - if you have $80 and the shoes cost $80 then it is sufficient that you have the $80 to pay for the shoes

  Its both sufficient and necessary. Anything less than $80 and you can no longer buy the shoes.

  With $10, it needs to be phrased like -I at least have $10 dollars. If I only had $10 I could no longer purchase the shoes.
• JinnyKim Alum Member

  January 2018 37 karma

  You guys are the best! Thanks so much