GMAT Prep RC: Dendrochronology, the study of tree-ring

[tim]

Let us know if there are any further questions on this one.

[RonPurewal]

Thanks very much Ron! Got it now.

Also, I should have noticed the strong tone of "only if" for an inference question.

well, "strong tone" isn't really the point -- the point is that "only if" is FUNDAMENTALLY DIFFERENT from "if".

it's basically the same thing as the difference between "necessary" and "sufficient".

i.e.,
X only if Y <—> Y is necessary for X
X if Y (If Y then X) <—> Y is sufficient to tell us X / for us to know X

you shouldn't memorize these, of course -- you should just UNDERSTAND why they are true. if you understand these things as well as you should, then these equivalences should be clear/obvious enough, with no need for memorization.

[amits428]

Hello experts,

I have a doubt regarding the first question 'The passage suggests which of the following
about the ring patterns of two trees that grew in
the same area and that were of different, but
overlapping, ages?'. I deduced option D as the answer because while the second paragraph tells us that 'these "complacent" rings tell nothing about changes in climate.' the first paragraph states that 'Often, ring patterns of dead trees of different, but overlapping, ages can be correlated to provide an extended index of past climate conditions.'

Cant option D be arrived at by combing these 2 information from the passage?

Regards,
Amit

[RonPurewal]

first -- and most importantly -- RC questions don't make you combine facts!
if you even THINK you have to do this, then, you are almost certainly headed down the wrong path entirely.

the principal skill tested in RC detail questions is finding things. once you've located something specific, out of a big long passage, you won't ALSO have to combine it with something else.

(combining statements is a skill that's tested in a different type of question -- specifically, "draw a conclusion/inference" questions in CR.)

__


the end of the first paragraph says: "Often, overlapping rings can tell us about changes in climate."
...then the second paragraph starts with, basically, "...But here's an instance in which they can't."

those rings still could be overlapping rings, of course. they just wouldn't tell us much about the climate.

[FeiyangC547]

Hi! Ron
I have a question. why B is wrong answer? I can not choose one between B and C when I was considering.

The passage is primarily concerned with
(A) evaluating the effect of climate on the growth of
trees of different species
(B) questioning the validity of a method used to study
tree-ring records
(C) explaining how climatic conditions can be deduced
from tree-ring patterns
(D) outlining the relation between tree size and cell
structure within the tree
(E) tracing the development of a scientific method of
analyzing tree-ring patterns

[RonPurewal]

B is wrong because it's wrong.

near the end of the passage the author describes a few cases in which the tree-ring method can't really be used -- but that certainly doesn't mean that the method itself is invalid!

[FeiyangC547]

Thanks a lot!
By the way, I found my reading skills very weak. Sometimes, I cannot answer questions correctly even I have know the whole passage well. Can you give me some pieces of advice on reading?

B is wrong because it's wrong.

near the end of the passage the author describes a few cases in which the tree-ring method can't really be used -- but that certainly doesn't mean that the method itself is invalid!

[RonPurewal]

if you actually "know the whole passage well" -- and you're not kidding about that -- then THAT'S THE PROBLEM, right there.

the whole point of RC is to "read" ONLY for the general structure and main themes of the passages—and to COMPLETELY IGNORE DETAILS, unless you actually get questions ASKING about those details (in which case you just go into the passage and FIND them).

if you are literally trying to understand and internalize ALL of the text in the passage... you're trying to something that's not only completely unnecessary, but also pretty much impossible in the timeframe that you actually have.
...so, in that case, it's no wonder you're overwhelmed.