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

Question

If a motor is sound-insulated, then it is quiet enough to use in home appliances. If a motor is quiet enough to use in home appliances, then it can be used in institutional settings. None of the motors manufactured by EM Industries are quiet enough to use in home appliances.

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

(A) If a motor can be used in institutional settings, then it is sound-insulated.
(B) None of the motors manufactured by EM Industries are sound-insulated.
(C) At least some of the motors manufactured by EM Industries can be used in institutional settings.
(D) If a motor is quiet enough to use in home appliances, then it is sound-insulated.
(E) None of the motors manufactured by EM Industries can be used in institutional settings.

Source: LSAT

KarishmaB · Accepted Answer

It is an if-then conditional statement. First check out this post: https://www.gmatclub.com/forum/veritas-prep-resource-links-no-longer-available-399979.html#/2012/1 ... tatements/ "If A, B" leads to A implies B and Not B implies not A. If a motor is sound-insulated, then it is quiet enough to use in home appliances. leads to A motor is sound-insulated means it is quiet enough to use in home appliances. Not quiet enough to use in home appliances means it is not sound-insulated. The argument tells us "None of the motors manufactured by EM Industries are quiet enough to use in home appliances". This means motors manufactured by EM Industries are not sound-insulated. Answer (B) Note that in case of if statements, "not A does not imply not B" So "not quiet enough to use in home appliances" does not imply "cannot be used in institutional settings". Hence answer is not (E)

nipun21 · Answer

I'm confused between options A, B and E. I took E. Kindly help

gmat1393 · Answer

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Bumping this post for discussion!

Srija221 · Answer

Why it can that NONE... quiet enough.... implies NONE.....Industrial setting?

Shishou · Answer

This stimulus has conditonal reasoning and may need a fair bit diagramming.
When conditional reasoning is used in must be true then the correct answer is the repeat form or the contrapositive.Every other inference is wrong.
A. Mistaken reversal- Wrong
B.Contrapositive-this is the correct answer 
C.variant of Mistaken Negation
D.Another mistaken reversal
E.Another mistaken negation

Shishou · Answer

Conditional reasoning is strange. If you start thinking through it you will start making real life inferences that theis not supported by the LSAT Stimuli.Questions with conditonal reasoning and mut be true need to be diagrammed

P@PU · Answer

Was confused between B & E . But all that differentiate is a little attentiveness only. Re read to find out the logic.

nurba92 · Answer

Conditional reasoning is some kind of magic. Don't reply to me, don't quote me. I am just happy that I finally started managing to solve 700 levels in CR (at least must be trues)

Ronit1997 · Answer

If you are brief with the concepts of discrete mathematics, you'll find this solution easy to follow:
Sound insulated -----> Home appliances (1)
Home appliances -----> Industrial Appliances
motor (EM industries) ------> NOT home appliances (2)
From (2) we follow that
home appliances -------> not (use) motor(EM industries) (3)

From (1) and (3) we follow
Sound insulated -----> not (use) motor(EM industries) 
and hence
motor (EM industries) ------> (are) not Sound insulated

I know this seems tedious but if P then Q condition should be crystal clear in your list of concepts to tackle these type of questions quickly

ChuHoaiNam · Answer

When do must be true question, i often draw a chart and it helps me a lot. If A, then B = A ->B. And we know contrapositive is correct. It means Not B -> Not A is correct. So apply this rule to this question:
A= a motor is sound-insulated
B= it is quiet enough to use in home appliances
C= it can be used in institutional settings
So, rewrite the stimulus we have: A - B; B->C ; and no motor manufactured byy.... is not B.

Answer analysis:
(A) If a motor can be used in institutional settings, then it is sound-insulated. rewrite C->A -> incorrect
(B) None of the motors manufactured by EM Industries are sound-insulated. rewrite not B->not A -> correct
(C) At least some of the motors manufactured by EM Industries can be used in institutional settings. -> incorrect
(D) If a motor is quiet enough to use in home appliances, then it is sound-insulated. -> B-> A -> incorrect
(E) None of the motors manufactured by EM Industries can be used in institutional settings. -> not B -> not C -> incorrect

Hence, B is correct. What if the stimulus does not have the if...then construction. i also pretend that it have this construction.

Thanks

bidskamikaze · Answer

If a motor is sound-insulated, then it is quiet enough to use in home appliances. If a motor is quiet enough to use in home appliances, then it can be used in institutional settings. None of the motors manufactured by EM Industries are quiet enough to use in home appliances.

If the statements above are true, which one of the following must be true?
  If A, then B ; If B, then C
X is not equal to B

(A) If a motor can be used in institutional settings, then it is sound-insulated.
-  There may be other types of motors that are not sound insulated, yet can be used in institutional settings.

(B) None of the motors manufactured by EM Industries are sound-insulated.
-  Correct.

(C) At least some of the motors manufactured by EM Industries can be used in institutional settings.
-  We cannot infer this.

(D) If a motor is quiet enough to use in home appliances, then it is sound-insulated.
-  There may be other motors that are not insulated, yet can be used in home appliances.

(E) None of the motors manufactured by EM Industries can be used in institutional settings.
-  The motors manufactured by EM Industries are not sound insulated, but they may have other motors that are perfect for institutional settings.

Answer B.

Namangupta1997 · Answer

Hi  KarishmaB

If "A implies B", then "not A implies not B" is false ? Why ? If cause doesn't happen, effect doesn't happen. What am I missing ?

(I read the article. It is still not 100% clear.)

KarishmaB · Answer

Multiple causes could lead to the same effect. 
If A then B just means that A is a cause that will lead to B. A is sufficient for B. But does it mean that if A doesn't happen, B will not? It doesn't mean that. It is possible that C causes B too. Hence 'not A' doesn't imply 'not B.'

'Only if A, then B' implies that A is necessary for B. So if A doesn't happen, B will definitely not happen.

VerbalBot · Answer

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

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

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