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Astronomer: Most stars are born in groups of thousands, each

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Astronomer: Most stars are born in groups of thousands, each [#permalink]

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2016 GMAT Official Guide, Question 2, Page 502

2. Astronomer: Most stars are born in groups of thousands, each star in a group forming from the same parent cloud of gas. Each cloud has a unique homogeneous chemical composition. Therefore whenever two stars have the same chemical composition as each other, they must have originated from the same cloud of gas.

Which of the following, if true, would most strengthen the astronomer's argument?

(A) In some groups of stars, not every star originated from the same parent cloud of gas.
(B) Clouds of gas of similar or identical chemical composition may be remote from each other.
(C) Whenever a star forms, it inherits the chemical composition of its parent cloud of gas.
(D) Many stars in vastly different parts of the universe are quite similar in their chemical compositions.
(E) Astronomers can at least sometimes precisely determine whether a star has the same chemical composition as its parent cloud of gas.
[Reveal] Spoiler: OA

Last edited by broall on 22 Sep 2017, 01:42, edited 1 time in total.
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Re: Astronomer: Most stars are born in groups of thousands, each [#permalink]

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New post 13 Jun 2015, 12:09
For option A, B, D and E---- We can say that "COULD BE". But we can't say that definitely as passage has no specific information for all of these options.


For this----- Therefore whenever two stars have the same chemical composition as each other, they must have originated from the same cloud of gas. to be true C has to be true.

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Re: Astronomer: Most stars are born in groups of thousands, each [#permalink]

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2016 GMAT Official Guide, Question 2, Page 502

2. Astronomer: Most stars are born in groups of thousands, each star in a group forming from the same parent cloud of gas. Each cloud has a unique homogeneous chemical composition. Therefore whenever two stars have the same chemical composition as each other, they must have originated from the same cloud of gas.

Which of the following, if true, would most strengthen the astronomer's argument?

(A) In some groups of stars, not every star originated from the same parent cloud of gas.
(B) Clouds of gas of similar or identical chemical composition may be remote from each other.
(C) Whenever a star forms, it inherits the chemical composition of its parent cloud of gas.
(D) Many stars in vastly different parts of the universe are quite similar in their chemical compositions.
(E) Astronomers can at least sometimes precisely determine whether a star has the same chemical composition as its parent cloud of gas.[/quote]

Explanation

Question Type: Strengthen
Boil It Down (Simplified & Abbreviated Summary of the Prompt): Each gas cloud unique -> If stars have same composition, came from same cloud
Missing Information: The stars take on the same fingerprint of the parent cloud
Goal: Based on the prompt, find the option that reinforces the missing information.

Analysis: This prompt seems fair enough. Each gas cloud has a UNIQUE, one of a kind signature, so it follows that any two stars must have come from the same parent cloud, but WAIT! Just because stars may have come from the same parent cloud, does that necessarily mean that the stars would reflect that truth? Not necessarily. That is the HUGE missing gap in the logic of this argument. No question, the right option needs to fill that void that the stars reflect the chemical makeup of the parent gas cloud.

A) Irrelevant. This argument isn't claiming that all stars that happen to be in a given group originated from the same cloud. Instead, the prompt is going the other direction. It's saying that if any two stars did come from the same parent gas cloud that they would have the same chemical signature. DUMP A!

B) Out of Focus. This option just presents a random fact that totally separate from the logic of the argument. The argument doesn't need support that similar clouds can be remote. Gone.


C) Yes! This was the exact missing link that we needed. The one piece of information that this argument lacks is that the stars take on an identifiable chemical signature from the parent cloud. C gives us exactly that. With C, we far more safely say that since the parent cloud has a UNIQUE chemical composition, AND with C, stars take take on that same chemical composition, that if two stars have the same composition as each-other, then they originated from the same cloud.

D) Violently Out of Focus. This option is talking about stars "quite similar in their chemical composition". The argument doesn't deal with stars that have a similar make up. The argument deals with stars that have THE SAME chemical make up.

E) Out of Focus. This option feels more like a correct option from an Inference question. As it relates to this strengthen question, however, the prompt actually makes it clear from the phrase "whenever" stars have the same chemical composition" that the ability to ascertain the composition is present. The argument doesn't need proof for something already established. Gone.

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Re: Astronomer: Most stars are born in groups of thousands, each [#permalink]

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New post 13 Jun 2015, 23:34
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2. Astronomer: Most stars are born in groups of thousands, each star in a group forming from the same parent cloud of gas. Each cloud has a unique homogeneous chemical composition. Therefore whenever two stars have the same chemical composition as each other, they must have originated from the same cloud of gas.

Which of the following, if true, would most strengthen the astronomer's argument?

(A) In some groups of stars, not every star originated from the same parent cloud of gas.
(B) Clouds of gas of similar or identical chemical composition may be remote from each other.
(C) Whenever a star forms, it inherits the chemical composition of its parent cloud of gas.
(D) Many stars in vastly different parts of the universe are quite similar in their chemical compositions.
(E) Astronomers can at least sometimes precisely determine whether a star has the same chemical composition as its parent cloud of gas.

Conclusion- whenever two stars have the same chemical composition as each other, they must have originated from the same cloud of gas.
Pre think step-In strengthen we can create a situation or a context in which the conclusion comes true or it increase the probability of success of the conclusion.With these in mind lets look at the answer choices

A-This is the opposite of what the argument states hence out of scope
B-Does not support the conclusion in any way
C-This is correct since it increases the chances that the conclusion will come true.As the star forms from its parent cloud gas it inherits(new info) the chemical composition of its parent cloud of gas hence it increases the possibility of success that they have must have originated from the same cloud of gas
D-Does not support the conclusion as it talks about stars in different parts of the universe.Stars of the universe is not the issue here
E-At least sometimes precisely determine" talks about determination of chemical composition which is out of scope.

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Re: Astronomer: Most stars are born in groups of thousands, each [#permalink]

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New post 09 Jun 2016, 23:34
EMPOWERgmatMax wrote:
2016 GMAT Official Guide, Question 2, Page 502

2. Astronomer: Most stars are born in groups of thousands, each star in a group forming from the same parent cloud of gas. Each cloud has a unique homogeneous chemical composition. Therefore whenever two stars have the same chemical composition as each other, they must have originated from the same cloud of gas.

Which of the following, if true, would most strengthen the astronomer's argument?

(A) In some groups of stars, not every star originated from the same parent cloud of gas.
(B) Clouds of gas of similar or identical chemical composition may be remote from each other.
(C) Whenever a star forms, it inherits the chemical composition of its parent cloud of gas.
(D) Many stars in vastly different parts of the universe are quite similar in their chemical compositions.
(E) Astronomers can at least sometimes precisely determine whether a star has the same chemical composition as its parent cloud of gas.


Explanation

Question Type: Strengthen
Boil It Down (Simplified & Abbreviated Summary of the Prompt): Each gas cloud unique -> If stars have same composition, came from same cloud
Missing Information: The stars take on the same fingerprint of the parent cloud
Goal: Based on the prompt, find the option that reinforces the missing information.

Analysis: This prompt seems fair enough. Each gas cloud has a UNIQUE, one of a kind signature, so it follows that any two stars must have come from the same parent cloud, but WAIT! Just because stars may have come from the same parent cloud, does that necessarily mean that the stars would reflect that truth? Not necessarily. That is the HUGE missing gap in the logic of this argument. No question, the right option needs to fill that void that the stars reflect the chemical makeup of the parent gas cloud.

A) Irrelevant. This argument isn't claiming that all stars that happen to be in a given group originated from the same cloud. Instead, the prompt is going the other direction. It's saying that if any two stars did come from the same parent gas cloud that they would have the same chemical signature. DUMP A!

B) Out of Focus. This option just presents a random fact that totally separate from the logic of the argument. The argument doesn't need support that similar clouds can be remote. Gone.


C) Yes! This was the exact missing link that we needed. The one piece of information that this argument lacks is that the stars take on an identifiable chemical signature from the parent cloud. C gives us exactly that. With C, we far more safely say that since the parent cloud has a UNIQUE chemical composition, AND with C, stars take take on that same chemical composition, that if two stars have the same composition as each-other, then they originated from the same cloud.

D) Violently Out of Focus. This option is talking about stars "quite similar in their chemical composition". The argument doesn't deal with stars that have a similar make up. The argument deals with stars that have THE SAME chemical make up.

E) Out of Focus. This option feels more like a correct option from an Inference question. As it relates to this strengthen question, however, the prompt actually makes it clear from the phrase "whenever" stars have the same chemical composition" that the ability to ascertain the composition is present. The argument doesn't need proof for something already established. Gone.
[/quote]

Hey Max,

What if option E says, Astronomers can every time find the composition of stars accurately. Will it be a correct answer. I think the problem with option E is can atleast sometimes. Please correct me if I am wrong.
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Re: Astronomer: Most stars are born in groups of thousands, each [#permalink]

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New post 12 Jun 2016, 10:43
Alok322 wrote:
2016 GMAT Official Guide, Question 2, Page 502

2. Astronomer: Most stars are born in groups of thousands, each star in a group forming from the same parent cloud of gas. Each cloud has a unique homogeneous chemical composition. Therefore whenever two stars have the same chemical composition as each other, they must have originated from the same cloud of gas.

Which of the following, if true, would most strengthen the astronomer's argument?

(E) Astronomers can at least sometimes precisely determine whether a star has the same chemical composition as its parent cloud of gas.

E) Out of Focus. This option feels more like a correct option from an Inference question. As it relates to this strengthen question, however, the prompt actually makes it clear from the phrase "whenever" stars have the same chemical composition" that the ability to ascertain the composition is present. The argument doesn't need proof for something already established. Gone.[/color]

Hey Max,

What if option E says, Astronomers can every time find the composition of stars accurately. Will it be a correct answer. I think the problem with option E is can atleast sometimes. Please correct me if I am wrong.

Hi Alok322,

I'd be happy to help. I like the idea of using hypotheticals with options to understand the logic backing up the argument, and the question.

So, let's run with your hypothetical:
Astronomers always have the ability to precisely determine whether a star has the same chemical composition as its parent cloud of gas.

That strengthens the notion that scientists can determine composition at will; HOWEVER, there's still a colossal shift in focus between the composition of the parent cloud vs the composition of the star. What if even though every CLOUD has a unique composition, the STARS that form from different clouds have standard compositions despite which cloud they formed from? The fact that this hypothetical still leaves such a glaring hole open leaves it remaining problematic.

Compare that to option C, which provides that missing link between composition of star and parent cloud (thus resolving that horrifically problematic gap within the argument).
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Re: Astronomer: Most stars are born in groups of thousands, each [#permalink]

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New post 15 Aug 2016, 22:25
Hi, I chose B rather than C. Here is my thought process:
I thought Strengthen must not be an Assumption.
Here the author already assumes that stars have same chemical pattern as their parent cloud. So I felt this to be the assumption.
So something other than assumption that helps strengthen the conclusion is what I chose.

(B) Clouds of gas of similar or identical chemical composition may be remote from each other.
If identical clouds are adjacent, assuming stars form with same imprint, analysing two stars will not lead to conclusion that these are formed from same cloud. So I chose this.

(C) Whenever a star forms, it inherits the chemical composition of its parent cloud of gas.
This is already the assumption on which the author relies. So I did not choose this.

Please correct my thought process.

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Re: Astronomer: Most stars are born in groups of thousands, each [#permalink]

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New post 22 Sep 2017, 01:23
[quote="LithiumIon"]2016 GMAT Official Guide, Question 2, Page 502

2. Astronomer: Most stars are born in groups of thousands, each star in a group forming from the same parent cloud of gas. Each cloud has a unique homogeneous chemical composition. Therefore whenever two stars have the same chemical composition as each other, they must have originated from the same cloud of gas.

Premise: Each Star is formed from the same parent cloud of gas.
And each cloud of gas has a unique homogeneous chemical composition.



Conclusion: Whenever two stars have the same chemical composition as each other, they must have originated from the same cloud of gas.


Pre-thinking: Clouds have unique composition --> Stars are formed from this cloud --> So, each star must inherit the properties of the cloud, else they would not have the same composition as the cloud from which it originated. --> If they inherit the same property then that would mean, any two stars from the same gas, would have the same competition.

Which of the following, if true, would most strengthen the astronomer's argument?

(A) In some groups of stars, not every star originated from the same parent cloud of gas.[If they don't originate from the same parent cloud of gas, then they would not have the same composition - this kind of acts as a weakener.]

(B) Clouds of gas of similar or identical chemical composition may be remote from each other.[The question is whether the stars have originated from the same cloud of gas or not -we are not concerned about the distance between these clouds of gas - eliminate this option. ]

(C) Whenever a star forms, it inherits the chemical composition of its parent cloud of gas. [This matches with our pre-thinking and this actually strengthens the argument,
by directly telling us that the stars inherit the property.If they inherit, then two stars with the same composition must come from the same cloud of gas.
]

(D) Many stars in vastly different parts of the universe are quite similar in their chemical compositions. [This does not help us in proving that two stars have come from the same cloud of gas - Eliminated.]

(E) Astronomers can at least sometimes precisely determine whether a star has the same chemical composition as its parent cloud of gas.[This is out of scope - we are not here to discuss whether Astronomers can determine something or not.]

Correct Answer C.
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Re: Astronomer: Most stars are born in groups of thousands, each   [#permalink] 22 Sep 2017, 01:23
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