QUESTION TEXT: If a motor is sound-insulated, then it…
QUESTION TYPE: Must be True
- Sound insulate (SI)–> Quiet for home (Q)
- Quiet for home (Q)–> Fine for institutions (I)
- Combined statement: SI –> Q –> I
I–> Q–> SI
- EM industries not quiet enough for home:
- Inference: EM industries not sound insulated:
ANALYSIS: Usually, you should draw “must be true” questions, using letters. I kept the words in the first two statements so they’re clear to you. But, the combined diagram above is how I actually draw.
After you make a diagram, the next step is to see how the fact about EM industries fits into the logical chain. Since EM is
Q, then they must be SI. You can and should be 100% certain about this kind of deduction on must be true questions, before checking the answers.
- This is an incorrect reversal of the first diagram.
- CORRECT. This is true, according to the contrapositive diagram above.
- We don’t know. Being quiet enough for the home is a sufficient condition for being useful in institutional settings. EM fails to meet this sufficient condition. Failing to meet a sufficient condition doesn’t tell you anything. It’s possible some EM motors are quiet enough for institutions, or it’s possible that none are.
- This is an incorrect reversal of the first fact. Sound insulation guarantees quiet, but something could be quiet even if it’s not insulated.
- This is an incorrect negation of the second fact. Even if something is not quiet enough for use in the home, it might still be quiet enough for institutional settings.
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