Q17 - Although Pluto has an atmosphere...

[sejin.park.214]

I don't understand why the "sun" would be at all relevant to this stimulus. There is no mention of it.

[timmydoeslsat]

I don't understand why the "sun" would be at all relevant to this stimulus. There is no mention of it.

The idea presented in the answer choice regarding the sun is relevant.

We have a sufficient assumption question stem. We want to prove the conclusion of "Pluto not being a true planet" true.

We do not have this kind of language of what constitutes a true planet. We can expect an answer choice that links up the evidence and this idea of true planet.

Answer choice E works here. We know from the evidence that Pluto formed an orbit around the planet Neptune.

And we love how answer choice E is structured:

True Planet ---> XXXXXX

We can expect the "XXXXXX" to represent evidence we have in the stimulus to arrive at the contrapositive.

Answer choice E states that a requirement of being a true planet is that it must form an orbit around the sun exclusively.

We know that this is not the case with Pluto, so we can arrive at the idea of ~True Planet.

[ptewarie]

This is one of those kind of strange questions that you see, but among closer investigation, you realize that it is not any different than any of the other "sufficient assumption" questions.

A little recap about sufficient assumption("assumed if")

1. You will have a premise
2. You will have a conclusion

Your goal is to allow the conclusion to occur with what is given to you.

the right answer choice will logically and FULLY connect the premise to the conclusion, in the sense that there IS NO POSSIBLE gap. You have to thus PROVE the conclusion with JUST the premise available.

So say I have this sentence:

Justin has won 3 trophies for soccer, so Justin is the best soccer player in his town.

Sufficient assumption: you can ONLY be the best soccer player in the town if you have won 3 trophies.

It's easy to see this because you have similar terms in both premise and conclusion. The way it works, is that the conclusion is ALWAYS the necessary portion of the sufficient assumption answer.

There's two ways it can be formulated:

Given Premise = A
Given Conclusion= B

How do we B from just A?
Simple, we say A->B

Then we have

P: A
P: A->B
which allows us to say B occured

OR you can have

P: A->B
C: A->D

How can we get A->D from A->B?
B->D


Anyways, in this problem:
Premise: Pluto formed in orbit around Neptune then ejected
Conclusion: Pluto is not a true planet.

So we have to find a way that notes that shows that orbiting around Neptune/being ejected from it --> ensured that Pluto is NOT a true planet

A: huh? not relevant
B: not relevant
c: We don't know this, and even if we did, it does not connect the conclusion to the premise
d. not relevant, we have no info

e says:
True planet--> Only if orbited exclusively around Sun
If NOT exclusively orbit around sun--> Not true planet.

Ok, what do we see in the contrapositive? The conclusion in the "neccesary portion"

Lets add this in to the stimulus:

Premise: Pluto orbit around Neptune then ejected

+ If NOT exclusively orbit around sun--> Not true planet.

Conclusion: Pluto is not a true planet.

Yep, we have a winner. Pluto orbited around Neptune, and this AC says that if you orbit around anything else but the sun, then you are not a true planet!!!

winner!

[timmydoeslsat]

So say I have this sentence:

Justin has won 3 trophies for soccer, so Justin is the best soccer player in his town.

Sufficient assumption: you can ONLY be the best soccer player in the town if you have won 3 trophies.

It's easy to see this because you have similar terms in both premise and conclusion. The way it works, is that the conclusion is ALWAYS the necessary portion of the sufficient assumption answer.

I love your post, but I wanted to point out this issue. This would not be a sufficient assumption. In this instance, we need something to bring us to the idea of best player in his town.

Your formulation is stating: best player in town ---> won 3 trophies. Your formulation is an only if statement, giving us a requirement of best player in town.

Other than that, this is a great post.

[hyewonkim89]

I still am really confused on this question..

I don't think I even understand the stimulus completely and I still have NO clue why the sun is in answer choices.

Will someone please break down the stimulus and go through all the answer choices?

Thanks in advance!

[rinagoldfield]

Great discussion above! I love the sufficient assumption recap, although I agree that the sufficient assumption in the trophy / soccer player analogy is that you can ONLY win three trophies if you’re the best soccer player in town. See: only if statements in the conditional logic chapter.

In terms of this question, here’s the argument core:

Pluto was a moon of Neptune at one point

-->

Pluto is not a true planet

What’s the gap? Well, the argument assumes that a celestial body that was a moon at one point can’t be a planet.

(E) gets at this sufficient assumption. It tells us that true planets have only ever revolved around the sun. In other words, they can’t have ever been moons of another planet. This is what we’re looking for!

(A) talks about simultaneousness... but Pluto was a moon BEFORE people called it a planet. No one ever thought it was a moon and a planet at the same time.

(B) is necessary but not sufficient.

(C) doesn’t get us to PLANET--definitely not sufficient.

(D) is out of scope. Size isn’t the issue.

Hope that helps.

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