Logical Reasoning

PT140 · S1 · Q17 If a motor is sound-insulated

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If a motor is sound-insulated, then it is quiet enough to use in home appliances.

Statements

When we read Must Be True paragraphs, we're primarily looking for Conditional, Quantified, or Causal wording.

All three claims here are Conditional / Quantified (if, if, none)

If.... Then.... Motor is sound quiet enough to use insulated in home appliances

If.... Then.... quiet enough to use can be used in in home appliances institutional settings

If.... Then.... manufactured not quiet enough to use by EM industries in institutional settings

Whenever we get more than one conditional, we check to see if any chain together. The 2nd sentence begins right where the the 1st one one leaves off, so they chain to give us this,

sound → quiet enough → can be used in insulated for home apps instit. settings

Then what about the last conditional?

made by EM → not quiet enough for home apps

The overlapping term is whether or not it's quiet enough for home appliances. In the chain, we say "it is quiet enough", but this last conditional is saying "it is not quiet enough". So let's contrapose the chain.

can't be used → not quiet enough → not sound in instit. settings for home apps insulated

According to this contrapositive chain, if something is "no quiet enough for home apps" then it is "not sound insulated".

We wouldn't be able to judge whether or not it can be used in institutional settings, since the chain doesn't flow to the left.

Goal

Most likely, the answer will reward our ability to chain together sentence 1 and sentence 2 if sound insulated, then can be used in institutional settings

or it will reward our ability to chain together sentence 1 and sentence 3, if manufactured by EM, then not sound insulated

17.

If the statements above are true, which one of the following must be true?

  1. If a motor can be

    Reversed Logic

    We know this: insulated → quiet enough → used in institutional This answer is acting like we know this: used in institutional → insulated That's moving illegally backwards.

    4% picked this

  2. Correct

    None of the motors manufactured

    Why this is right

    The last sentence says manufactured → not quiet enough by EM Industries for home appliances The first sentence says not quiet enough → not sound for home appliances insulated If we put those two ideas together, we get made by → not quiet → not sound EM enough 4 home insulated

    Skill tested: Must be True · how this choice captures the argument's function is the move to repeat next time.

    60% picked this

  3. At least some of the

    Almost Contradicted

    The only way we have available to prove that something can be used in institutional settings is to establish that "it's quiet enough to use in home appliances". But we were told that none of the EM motors are quiet enough to use in home appliances, so we don't have any way to prove that they can be used in institutional settings. Some people may have picked this out of confusion based on our chain: can't be used → not quiet enough → not sound in instit. settings for home apps insulated But there's no way to derive that some EM motors (all of which are not quiet enough) can be used in institutional settings.

    1% picked this

  4. If a motor is quiet

    Reversed Logic

    This just reads the first sentence in an illegal backwards motion. Given If Don is in Texas, then Don is in America. that doesn't prove that If Don is in America, Don is in Texas. We were told if sound insulated, then quiet enough and this answer is pretending we can derive if quiet enough, then sound insulated

    4% picked this

  5. None of the motors manufactured

    Opposite Logic

    We weren't given any way to prove that something can't be used in institutional settings, only a way to prove that something can be used. We might pick this out of confusion about what we can infer out of the contrapositive chain: can't be used → not quiet enough → not sound in instit. settings for home apps insulated Given a chain like, ~A → ~B → ~C If we say "none of the motors from EM are B", then we can say motor from EM → ~B → ~C But we can't infer anything backwards to know anything about A. We know that none of the EM motors are quiet enough, but this answer is assuming that "if you're not quiet enough, then you can't be used in institutional settings". We were only told, "if you are quiet enough, then you can be used".

    31% picked this

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