Critical Reasoning

Another one...

I see very hard queztion. pls, help

A and D are quite close.Will go aith A.

A - is a fact.

IMO - D

B looks like a contender to me Dana.

Actually, it's A. I was pretty annoyed by this question, since it's not the complexity of the issue that brings you down, but the wording.

I'd also like to see explanations on why this is the correct answer.

I dont see A as a Assumption.It just says a fact.

Wordings..OMG terrible

But then, what about "B"
It says that most stars that are too cool to burn hydrogen are too cool to burn lithium completely. This is the assumption, I reckon! Isn't it?

DanaJ wrote:Another one...

DanaJ,
I think some typo between lethium and helium here. If that is not the case then its confusing.

Only support for A or E is statement, the conclusion involves any/all so none of the options using most or many will be a correct option. Since E is obviously incorrect that left us with only A, that said I am puzzled with helium vs lethium here.

HI EVERY ONE

HERE IS THE EXPLAINATION:

A says that none of the coolest brown stars has ever been hot enough to convert lithium into helium.

that is, this option uses the most important techniue ( ALTERNATE DO NOT EXIST)of assumption questions to fill the gap between the evidence and the conclusion( i.e any star that do not have lithium is not a coolest browwn star.)

Therefore, according to A if in whole world history coolest brown stars have never been atleast too hot to convert lithium into hilium, the conclusion that the stars not having the lithium are not coolest brown stars always holds.

@Dana

plz go thru my explanation.

In many ways u have been very much instrumental in my GMAT Journey. One is your steallar score!! the moment I see that figure, My spirits rise up!! Viens get hotter!!

Second is ur pic that u have posted..I would have seen that not less than 1000 times to figure out what does that pic mean..I see a gal on a Bicycle or a cat standing near a lampost on a Bicycle...(very crappy visualisation of mine).Plz tel what doe sthat pic stand for!

Coming to answer, I used Negation technique to figure out whether conclusion falls apart or not!!

negating A, conclusion falls apart.

stars when first formed contains substantial amount of lithium
all stars but the coolest of the brown drawfs are hot enough to destroy lithium completely by converting it to helium------->

the coolest of the brown drawfs are not hot enough to destroy lithium completely by converting it to helium----->
these coolest stars contains lithium

conclusion: any star which contains no lithium does not belongs to these coolest star

any is the clue which suggest that the author supposes that none of the coolest brown drawf has ewver been hot enough to destroy lithium........

use of any makes the conclusion very strong and therefore we need equally strong assumption

which is A

Hey gmatmachoman - your explanation actually makes sense, you know! Indeed, if you negate a statement and this makes the argument fall apart, then it's definitely the assumption you are looking for.

I initially had a picture of my head on the forum, I'm attaching it here so you can see it. But then I decided at some point that I wanted to be "anonymous" so I chose to crop a picture of a statue, because I needed some sort of "flag" to be able to spot my posts fast. This picture was taken at the Peles Castle, near Brasov. It's one of the most famous castles in my country - actually, we don't have that many, so it's probably one of the few well preserved castles apart from the so-called Dracula's Castle, in Bran. I've cropped the statue in the right hand side of the thing...

@DanaJ

Thx for clearing the cobwebs swirling ard the pic! Now I wont visualise anything like gal on bicycle!!HAhaha.!

Well Gmatmachoman asked me to answer this question.

Conclusion: Any star that does not contain lithium -> not a brown dwarf

Premise: All stars, except brown dwarfs, are hot enough to destroy lithium completely.

Please note: the statements with hydrogen are just background information. Remember, our conclusion does not depend on the background info but is based on the premise.

Make a probability indicator in the conclusion: ANY

A-> None of the brown stars are hot enuf to burn the lithium completely. The probability indicator - None makes the author to draw a conclusion on ALL/ ANY star that does not contain lithium. Correct

B-> The first thing i noticed in this answer choice was the probability indicator- Most. Remember the conclusion draws a statement on ANY star. this is an extrapolation and does not stand true.
for eg: suppose there are 100 students in a college.
Most implies atleast 51. so lets suppose that 51 students drink coffee.
With this information can i conclude that all the 100 students drink coffee?
Well answer choice B makes this mistake. Hence Eliminated!

C-> Brown dwarfs capable of destroying helium is not our point of issue. Note that the conclusion talks about only lithium and not helium.

D-> This does not matter. Let them be formed with the same percent of lithium but whether all brown dwarf stars use up the lithium completely or not is the question at issue. Eliminated!

E->Let brown dwarfs be similiar to red dwarfs in terms of appearance. does it mean they all extinguish the lithium resources completely? remember all that glitters is not gold. just becoz something is similiar to gold in appearance, can we determine that both the objects are gold? Eliminated!

@ Dana, what is the source of this question? interesting one!