Urban air contains more sulfur dioxide than does rural air

[RonPurewal]

I am having trouble with CR, not knowing if I should just let my mind flow in GMAT's logic way, forcing myself to accept the right answer, or I should stick to my own thinking and try to defend for myself, in which case I may enhance my GMAT-wrong thinking capability.

Please help.

not sure what you mean here.
if "defend myself" (nb: "defend for" is not proper english) means "i should try to argue against GMAC's official answers", then, no, of course that would be a waste of your time.
their correct answers are correct. if you disagree with their correct answers, then they're right and you're wrong.

maybe i'm misunderstanding you here, because, to me, it seems that you're asking this: "should i try to think in the same way the problems work, or should i try not to think in the same way the problems work?"
... i mean, the answer to that one is the most obvious thing in the world, so i doubt that's what you are asking. so, perhaps you could rephrase your question.

--

also, note that there's really no such thing as "GMAT logic". I.e., "GMAT logic" is normal real-world logic.

there is nothing on the CR section that requires any obscure/esoteric/special GMAT-only type of reasoning. in fact, this is the entire point of the CR section: you just have to use normal thought processes that have already exist in your head for many years. the main challenges are (i) engaging with the passages enough to understand them and (ii) staying focused on the issues in the problems.
but, thinking that the GMAT uses some special, mystical, unique brand of logic is a big mistake. it's the same kind of logic that people use every single day ... everywhere, except classrooms.

[lindaliu9273]

Hi instructors,

For CR, I always first look at the question to decide what type of question it is and what's the goal.

But for this question, I'm a little confused.
"be most important to take into account in evaluating the result?"
Should we choose "weaken" option, or "explain" option? I spend some time thinking but don't have certain answer.

[RonPurewal]

Hi instructors,

For CR, I always first look at the question to decide what type of question it is and what's the goal.

But for this question, I'm a little confused.
"be most important to take into account in evaluating the result?"
Should we choose "weaken" option, or "explain" option? I spend some time thinking but don't have certain answer.

Ultimately, they're the same. They differ only in superficial ways.

As usual, it's easiest to show this by way of examples.

My friend, whose weight has been the same for years, has started eating more food than ever before. Therefore, he will gain weight.
WEAKEN THIS ARGUMENT:
e.g.,
... He's working out more now
... He's eating different food (that is less conducive to weight gain)
... He's sick and throws up a large amount of what he eats now
... He just started a drug that speeds metabolism (or stopped a drug that slows it)
Etc.

My friend, whose weight has been the same for years, has started eating more food than ever before. However, he is not gaining weight.
EXPLAIN THIS UNEXPECTED FINDING:
e.g.,
... He's working out more now
... He's eating different food (that is less conducive to weight gain)
... He's sick and throws up a large amount of what he eats now
... He just started a drug that speeds metabolism (or stopped a drug that slows it)
Etc.

They're the same.
So exactly, in fact, that I was able to literally copy and paste the "weakeners" as "explanations".

The differences are superficial:
- The "weaken" problem is presented as an argument, because the events in question have not actually happened yet. It's about predictions.
"- The "explain" problem, on the other hand, is presented as a set of factual observations. It's not (or is no longer) an argument, because the events in question HAVE happened. It's about retrospective explanations.

Those might sound different. But, in terms of actual thought processes, any and all differences are immaterial.
If "x" is a reason to predict that something might not happen ("weaken")... then, later, in retrospect, the same "x" could be a reason why that thing didn't happen.

So... call it "explain"; call it "weaken"; heck, call it "pink flamingo dust", if you want. Just make sure you understand the nature of the task and don't become overly preoccupied with labels.

[tronghieu1987@gmail.com]

I found the structure of the stimulus in this questions really ambiguous.

It starts with this sentence "Urban air contains more sulfur dioxide than does rural air, and plants in cities typically grow more slowly than do plants in rural areas"
Firstly, I too think that the second clause (after , and) is a minor conclusion that draws on the first clause. But wait, they are 2 INDEPENDENCE CLAUSE, and from the purpose of the experiment, I have a second though that they are 2 different claims we need to prove in the experiment: plants in air with SO2 grow more slowly than those in low SO2 air, and plants in urban area grow more slowly than those in rural are.

After that, I read the remaining of the stimulus. It says that an experiment is conducted to see the difference in growth is due to SO2. And the result of this experiment, which is conduced in a free-SO2 environment, is that the plants in urban greenhouse grew more slowly than did those in rural greenhouse. So I think, what is the difference due to S02: the result shows nothing about this. And the only thing I can draw from the result is that in the same environment (SO2 free), plants in urban area grew more slowly than those in rural area did.. Ok, then the second claim in the first sentence is proved.

So in order to prove the first claim about the difference due to SO2, I need to know other result of the experiment. And choice B does give this result. It proves that no matter what area of the plants, the plants in the non-free SO2 environment grow more slowly than those in free SO2 environment. That's enough for us to evaluate the result of the experiment.

[RonPurewal]

"xxxx typically happens" is NOT a 'conclusion' or 'hypothesis'. it's a FACT that has been directly observed: in most cases ("typically"), xxxx happens.

if such a thing is stated at the beginning of a passage, then, almost invariably, the rest of the passage will be concerned with explaining WHY "xxxx typically happens". (but there's no doubt at all about WHETHER xxxx happens—it's a fact!)

[RonPurewal]

see also problem #116 in the OG (13th / 2015 edition), which starts in the same way: Scientists typically do xxxxx (FACT.)

the entire remainder of the passage is dedicated to a debate over WHY "scientists typically do xxxxx". it's a FACT that they typically do xxxxx, but we can still debate why that is so.