LSAT 103 – Section 1 – Question 09

LSAT 103 - Section 1 - Question 09

September 1998

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Question
QuickView		 Type Tags Answer
Choices		 Curve Question
Difficulty		 Psg/Game/S
Difficulty		 Explanation
PT103 S1 Q09
+LR
+Exp
Weaken +Weak
A
0%
153
B
90%
165
C
2%
155
D
8%
157
E
1%
160
135
144
153
 +Medium 147.884 +SubsectionMedium

Kevin’s explanation

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Measurements of the motion of the planet Uranus seem to show Uranus being tugged by a force pulling it away from the Sun and the inner planets. Neptune and Pluto, the two known planets whose orbits are farther from the Sun than is the orbit of Uranus, do not have enough mass to exert the force that the measurements indicate. Therefore, in addition to the known planets, there must be at least one planet in our solar system that we have yet to discover.

Summarize Argument: Phenomenon-Hypothesis
The author concludes that there must be at least one undiscovered planet in our solar system. This is because measurements show that Uranus is being pulled away from the Sun by some force, and the planets further from the Sun than Uranus are too small to provide that force.

Notable Assumptions
The author assumes that a planet must be providing the force pulling Uranus away from the Sun. This means he doesn’t believe the force could from any other celestial object. The author also assumes that Neptune and Pluto couldn’t together provide the necessary force to pull Uranus away from the Sun.

A
Pluto was not discovered until 1930.
It doesn’t matter when Pluto was discovered. We need to weaken the idea that there findings around Uranus mean there’s an undiscovered planet in our solar system.
B
There is a belt of comets beyond the orbit of Pluto with powerful gravitational pull.
Even though Pluto and Neptune lack the mass to pull Uranus away from the Sun, there’s a belt of comets behind Pluto fully capable of doing so. This suggests that the author’s “another planet” hypothesis has overlooked an important fact.
C
Neither Neptune nor Pluto is as massive as Uranus.
We already know Neptune and Pluto don’t have the mass to pull Uranus away from the Sun. This doesn’t challenge anything in the author’s argument.
D
The force the Sun exerts on Uranus is weaker than the force it exerts on the inner planets.
This is probably true, but it doesn’t matter. We need to challenge the “another planet” hypothesis the author arrives on.
E
Uranus’ orbit is closer to Neptune’s orbit than it is to Pluto’s.
Neither planet has the adequate mass to pull Uranus away from the Sun. This leaves the door open to the author’s hypothesis.

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LSAT PrepTest 103 Explanations

Section 1 - Logical Reasoning

Section 2 - Logical Reasoning

Section 3 - Logical Reasoning

Section 4 - Reading Comprehension

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