inequality problem from May 27, 2010 study hall

[AsadA969]

Source:
Thursdays with Ron on May 27, 2010 study hall
https://vimeo.com/12233170
when the tutorial's time is running on 01:32:45 hour...

Is m+z>0
(1) m-3z>0
(2) 4z-m>0

5*1st statement-----> 5m-15z>0
4*2nd statement----> 16z-4m>0
………………………………………………..
Add up-------> m+z>0
So, sufficient!


Ron, is it ‘C’ trap question? I mean the correct answer is NOT “C”?? also, I didn't understand WHY the quick stunt is discussed there. Could you help me by giving your explanation (about the relation between the topic and the quick stunt), please?
Thanks...

[tim]

Something is only a C trap if you look at the two statements and immediately KNOW that combining them will give you a unique answer to the question at the top. You did not have that realization (or else you wouldn't have asked about the trick in this post), so this is NOT a C trap for you.

As for the last part of your post, the simple answer to your "why?" question is because it works. I suspect that's not the question you intended to ask, so if you ask the question you really meant to ask we'll be happy to help you further.

[RonPurewal]

Ron, is it ‘C’ trap question?

the answer is C, so, clearly it's not a C-trap.

I didn't understand WHY the quick stunt is discussed there.

only for fun.
obviously, you will never HAVE to randomly multiply things by 4 and 5 for no apparent reason. (there will NEVER be any "lightbulb moment" problems on this exam; you should not need "random" or "divinely inspired" steps to solve the problems.)

[AsadA969]

Something is only a C trap if you look at the two statements and immediately KNOW that combining them will give you a unique answer to the question at the top.

Is (x-2) (x-3)>0?
1) x-2>0
2) x-3<0

after, combing the two statements i can immediately know the unique answer to the question at the top. so, this one is "C trap" question, right tim?

[RonPurewal]

where is this problem even coming from? did you just make it up?
(with the x-2 and x-3 terms in it)

the official exam would not present you with such a problem.

__

do note, by the way, that "x – 2 < 0" would be sufficient alone.

also, "x – 3 > 0" would be sufficient alone.

[AsadA969]

where is this problem even coming from? did you just make it up?
(with the x-2 and x-3 terms in it).

Ron, i just make creativity this question from the below link:
https://www.manhattanprep.com/gmat/foru ... 32914.html

the official exam would not present you with such a problem.

Ron, i've a curiosity to know WHY official exam would not present this sorta problem? i've maintained all the things, which you told in the following link.

Ron, you said in the following link (in your last comment) that ''you will always NEED at least one of the statements.''.
https://www.manhattanprep.com/gmat/foru ... 32936.html

[tim]

I'd be curious to hear from Ron why the GMAT wouldn't give a problem like this. As far as it being a C-trap, please note that Ron and I have used different implicit definitions in our posts. Ultimately it doesn't matter, because whatever term you use you need to know what to watch out for. In this case, once you realize that combining the two statements will give a unique answer to the question, you immediately know that E is not the answer, but you NEED TO BE CAUTIOUS. In other words, you need to carefully evaluate whether either statement alone is sufficient rather than just blindly choosing C.

[RonPurewal]

i'm talking about this problem, which comes from God-only-knows what source:

Is (x-2) (x-3)>0?
1) x-2>0
2) x-3<0

this problem would never appear on the exam because it works exactly like this:
Is xy > 0?
1) x > 0
2) y < 0

note:

a/
it's way too easy.
(this isn't a matter of opinion. if you compare this problem to the FIRST 10-20 problems in the official guide, you'll notice that this one is still way, way easier than all of those.)

b/
this problem doesn't depend in any way on anything about the actual content chosen.
literally, if we get rid of (x – 2) and (x – 3) and replace them with "x" and "y", it makes no difference.

c/
someone who isn't paying any attention to the goal of the problem is very likely to still get this one correct. ("oh hey, there's an (x – 2), and there's an (x – 3), i guess i probably need them both.")

[RonPurewal]

by contrast, consider the following 2 versions of the problem:


Is (x – 2) (x – 3) > 0?
1) x – 2 < 0
2) x – 3 < 0
(answer = A)

or

Is (x – 2) (x – 3) > 0?
1) x – 2 > 0
2) x – 3 > 0
(answer = B)

either of THESE two versions COULD absolutely be an official problem. notice the difference -- and notice that NONE of the 3 complaints above applies to either of them.

a/ these aren't as easy as the first one, and they aren't as easy as the first bunch of problems in the book, either.

b/ the answers to these problems depend VERY specifically on the (x – 2), the (x – 3), and the directions of the inequalities in the statements. if we just put "x" and "y" in place of (x – 2) and (x – 3), the problems don't work anymore.

c/ to get these problems correct, you need a keen sense of THE GOAL. unless you know EXACTLY what you are trying to do in these versions, you'll get them wrong.

[tim]

Very interesting. Thanks for the insight, Ron!

[RonPurewal]

Very interesting. Thanks for the insight, Ron!

sure.