Planetary Systems - confusing CR

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GMIHIR: Junior | Next Rank: 30 Posts; Posts: 18; Joined: Mon Jan 09, 2012 8:23 pm

by GMIHIR » Wed Apr 18, 2012 9:04 pm

When a planetary system forms, the chances that a planet capable of supporting life will be formed are high. The chances that a large planet the size of Jupiter or Saturn will be formed, however, are low. Without Jupiter and Saturn, whose gravitational forces have prevented Earth from being frequently struck by large comets, intelligent life would never have arisen on Earth. Since planetary systems are unlikely to contain any large planets, the chances that intelligent life will emerge on a planet are, therefore, low.
Knowing which one of the following would be most useful in evaluating the argument?
(A) whether all planetary system are formed from similar amounts of matter
(B) whether intelligent species would be likely to survive if a comet struck their planet
(C) whether large comets could be deflected by only one large planet rather than be two
(D) how high the chances are that planetary systems will contain many large comets
(E) how likely it is that planetary systems containing large planets will also contain planets the size of Earth

Can anyone please explain and confirm what the OA is? Thanks.

Source: Beat The GMAT — Critical Reasoning | Wed Apr 18, 2012 9:04 pm

sam2304: Legendary Member; Posts: 1239; Joined: Tue Apr 26, 2011 6:25 amFollowed by: 26 members; Thanked: 233 times; GMAT Score:680

by sam2304 » Wed Apr 18, 2012 9:17 pm

When a planetary system forms - high chances of planet supporting life forms and low chances of large planets. Large planets save planets with life forms by attracting large comets. Since large planet formation is low, life forms emerging on a planet is low.

A - irrelevant
B - question of survival - not necessary now
C - no of large planets is irrelevant
D - This seems fine. If the chances are high then life forms emerging on a planet is low, if it is very low then life forms emerging on a planet is high.
E - Irrelevant.

The underlying assumption is if formation of large planet is low then large comets will frequently hit the small planets preventing the emergence of life forms. So we got to find how frequently the small planets will be hit by comets

IMO D.

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killer1387: Legendary Member; Posts: 581; Joined: Sun Apr 03, 2011 7:53 amFollowed by: 5 members; Thanked: 52 times

by killer1387 » Thu Apr 19, 2012 12:16 am

will go with sam

would like to make a point regarding
option B: whether intelligent species would be likely to survive if a comet struck their planet

this option is already addressed in the argument which says"the frequency is decreased" and hence they are surviving somehow in spite of some attacks.
so B is incorrect.

Birottam Dutta: Master | Next Rank: 500 Posts; Posts: 342; Joined: Wed Jul 08, 2009 8:50 amFollowed by: 19 members; Thanked: 214 times; GMAT Score:740

by Birottam Dutta » Thu Apr 19, 2012 5:32 am

The argument here is that large plants are required to enable life on small planets by preventing comets from hitting the small planets.

In all the options, D is the best choice because D asks how many comets will be found in the planetary systems. This information is required to evaluate the argument.

A is out of context
B is close but here as mentioned above the answer is implicitly provided in the passage itself.
C and E are irrelevant.

Hence, D!

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GMATGuruNY: GMAT Instructor; Posts: 15539; Joined: Tue May 25, 2010 12:04 pmFollowed by: 1906 members; Location: New York, NY; Thanked: 13060 times; GMAT Score:790

by GMATGuruNY » Thu Apr 19, 2012 7:47 am

GMIHIR wrote:When a planetary system forms, the chances that a planet capable of supporting life will be formed are high. The chances that a large planet the size of Jupiter or Saturn will be formed, however, are low. Without Jupiter and Saturn, whose gravitational forces have prevented Earth from being frequently struck by large comets, intelligent life would never have arisen on Earth. Since planetary systems are unlikely to contain any large planets, the chances that intelligent life will emerge on a planet are, therefore, low.
Knowing which one of the following would be most useful in evaluating the argument?
(A) whether all planetary system are formed from similar amounts of matter
(B) whether intelligent species would be likely to survive if a comet struck their planet
(C) whether large comets could be deflected by only one large planet rather than be two
(D) how high the chances are that planetary systems will contain many large comets
(E) how likely it is that planetary systems containing large planets will also contain planets the size of Earth

Can anyone please explain and confirm what the OA is? Thanks.

This passage makes a common assumption: TRUE FOR ONE = TRUE FOR ALL.
The premise is about the EARTH: Without Jupiter and Saturn, whose gravitational forces have prevented Earth from being frequently struck by large comets, intelligent life would never have arisen on Earth.
The conclusion is about OTHER PLANETS: Since planetary systems are unlikely to contain any large planets, the chances that intelligent life will emerge on a planet are, therefore, low.
The assumption is that ALL PLANETS with intelligent life need to be protected from large comets.

Only answer choice D would help us determine the validity of this assumption: how high the chances are that planetary systems will contain many large comets.

The correct answer is D.

Answer choice B is out of scope. Whereas B discusses what is needed for intelligent life to SURVIVE, the passage draws a conclusion about what is needed for intelligent life to EMERGE -- a very different concept.

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klmehta03: Senior | Next Rank: 100 Posts; Posts: 74; Joined: Sun Sep 05, 2010 3:11 pm; Thanked: 3 times

by klmehta03 » Thu Apr 19, 2012 1:40 pm

Hi Mitch,
Nice explanation. I was down to D or E. I chose E can you please explain why E is incorrect?
Thanks in advance
K

vk_vinayak: Legendary Member; Posts: 502; Joined: Tue Jun 03, 2008 11:36 pmFollowed by: 21 members; Thanked: 99 times

by vk_vinayak » Thu Apr 19, 2012 9:06 pm

Hi,

According to the passage, for intelligence life to emerge on a planet, the planet must be protected from frequent collisions from comets. The size of the planet is immaterial for an intelligent life to emerge on a planet. Hence E is not correct.

- VK

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