duongthang wrote:we know that an argument can have many assumption and we are asked usually of one of the assumptions or a weakener or strengthener of one of those assumptions.

EXPERT, PLS, HELP HERE.

Please, give me an argument and show me 2 assumptions which, together with the evidence, help make conclusion. Please, do this, then I will present more questions.

Of course I'm No Expert. Feel free to disregard my post.

This month, Library X changed it's past-due fees on books checked out by patrons. The past-due fee (per day book is past due) decreased from 20 cents to 10 cents. This month, Library X's revenue from fees increased by twenty percent even though the number of patrons remained constant. Thus, the revenue increase is mostly due to patrons checking out more books on average this month than last month.

Evidence + [ Assumptions ] = Conclusion

Necessary Assumptions:

1. Patrons did not hold on to library books, past their due dates, longer (on average) this month; holding the number of books checked out constant.
2. Revenue from Library DVD rental fees did not increase from 17 percent (last month) to 29 percent (this month).

Both assumptions together help the argument because they rule out those possible explanations for the increase in revenue (from fees). However, if either assumption is negated, the argument will no longer hold because the conclusion will not follow from the evidence provided.

Any more assumptions? (Sufficient / Necessary) ?

Thank you Xlogic. For me " expert" means a person who knows clearly of the point anh you are an expert to me already. Any one know someting can be an expert.

SUFFICIENT assumption is explained in an article in this forum. I think we do not need to know. WE need to know necessary assumption and its negation test. You wonderfully give me the two.

THE POINT I WANT TO MAKE HERE IS THAT HARD-TO-SEE ASSUMPTION CREATES HARD WEAKENER/STRENGTHENER OR ANY KIND OF QUESTION WHICH IS BASED ON ASSUMPTION.

Now, I can create 2 weakeners based on the 2 assumptions.

1. persons keep the book past the due date longer.
2. Revenue from dvd reatal of library increase substantially.

ASSUMPTION BASED QUESTIONS is center of the CR section of gmat. The correct answer choice of these question must relevant to an assumption. ANALIZE EACH ANSWER CHOICE TO SEE WHETHER IT IS RELEVANT TO AN ASSUMPTION IS A GOOD METHOD TO ATTACK HARD QUESTIONS.

figuring out an aasumption before going to answer choice is not effective because the weakener may be relevant to not to the assumption we figure out but to another assumption.

Xlogic, can you give me one more necessary assumption which is hard to see.

duongthang wrote: figuring out an aasumption before going to answer choice is not effective because the weakener may be relevant to not to the assumption we figure out but to another assumption.

I totally agree with this statement. Because there are usually numerous necessary assumptions for any CR passage, it is not efficient to pre-phrase an exact necessary assumption before going to the answer choices. At best, we should have a general idea of what the necessary assumption will do to defend the argument before going to the answer choices. (Maybe we can get some expert advice on my last point)

duongthang wrote: Xlogic, can you give me one more necessary assumption which is hard to see.

Here are two more:

The author assumes that...
1. Of all the books checked out this month, at least some of them were held (by patrons) past their due dates
2. Of all the books checked out and were past due this month, the Library collected at least some of the past-due fees from patrons this month.

@duongthang: For practice, you think you could generate CR type "answer choices" for this question?
It could be a strengthen/weaken, assumption or flaw question type.

What do you think?

The author assumes that...
1. Of all the books checked out this month, at least some of them were held (by patrons) past their due dates
2. Of all the books checked out and were past due this month, the Library collected at least some of the past-due fees from patrons this month.

I do not thing they are assumptions

I want to show that hard weakener/strengthener is based on hard to see assumption. Please, give me hard to see assumption so that I can create hard weakener.