Question about the LSAT question!

This topic has expert replies
Junior | Next Rank: 30 Posts
Posts: 20
Joined: Tue Feb 02, 2010 8:32 am
Thanked: 14 times
Followed by:6 members
GMAT Score:760

Question about the LSAT question!

by Eldorjon » Mon Feb 08, 2010 4:33 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 of 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 systems are formed from
similar amounts of matter

(B) whether intelligent species would be likely to
survive if a comet stuck their planet

(C) whether large comets could be deflected by only
one large planet rather than by 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

[spoiler]OA is D

I got this wrong, because there is no implication that the comets that struck the Earth come from within the planetary system. Even it is determined that there is very low chance that planetary systems contain large comets, it may possible that large comets will strike the planet from outside the system.

Test for evaluate questions is whether polar opposite answers to the answer choice produce opposite effects on the argument, i.e. strengthen and weaken. If it was stated in the stimulus that comets that might strike the Earth came mainly, or even partially, from within the planetary system D would be undoubtedly the correct answer.

Can the answer like this weaken the argument? Any explanations are appreciated![/spoiler]
Source: — Critical Reasoning |

User avatar
Master | Next Rank: 500 Posts
Posts: 293
Joined: Thu Jan 14, 2010 9:08 am
Location: India
Thanked: 36 times
Followed by:5 members
GMAT Score:730

by mohit11 » Wed Feb 24, 2010 10:00 pm
Well, The answer should be D by POE, let me illustrate..


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 of 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.

WHEN -- Planetary system forms - Chances that a planet that will support life is High and chances of large planets being formed are Low.

HOWEVER - Without large planets, Comets would have hit earth and prevented any chances of intelligent Life to arise on earth.

THEREFORE - Since chances of large planets to formed are low, therefore comets are more likely to hit earth, therefore chances that intelligent life will emerge on a planet is low


Knowing which one of the following would be most
useful in evaluating the argument?

(A) whether all planetary systems are formed from
similar amounts of matter - So how does this help? Even if they are formed of the same matter or are not formed does not affect our argument at all - OUT

(B) whether intelligent species would be likely to
survive if a comet stuck their planet - Survival of intelligent species is not in question, the fact that intelligent life will come into existence or not is the question. - OUT

(C) whether large comets could be deflected by only
one large planet rather than by two - Even if large planets could be deflected by one large planet, it still does not help us evaluate the argument. OUT


(D) how high the chances are that planetary systems
will contain many large comets - Ok lets consider two options, chances are high and chances are low, if chances are high then they will most definitely deflect comets and intelligence life will come into existence, however, if chances are low, comets will hit planets like earth and even though initially chances were high eventually intelligent life will not come into existence. Directly affects our argument and hence is our answer. But lets look at E

(E) how likely it is that planetary systems containing
large planets will also contain planets the size of
Earth - We are not talking about size of earth , further even if chances are high or low for that matter. it does not affect our argument. Hence out of scope.

Hope it helps :)