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# If x > y, is zx > yx?

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Intern
Joined: 23 Jul 2012
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Concentration: Finance, Strategy
GMAT 1: 560 Q37 V28
GPA: 3.75
WE: Accounting (Accounting)
If x > y, is zx > yx? [#permalink]

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30 Jul 2012, 19:13
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If x > y, is zx > yx?

(1) z > 0

(2) y < 0
[Reveal] Spoiler: OA
Math Expert
Joined: 02 Sep 2009
Posts: 39673
Re: If x > y, is zx > yx? [#permalink]

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31 Jul 2012, 01:13
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If x > y, is zx > yx?

Is $$zx > yx$$? --> is $$zx-yx>0$$? --> is $$x(z-y) >0$$?

(1) z > 0. Clearly insufficient.

(2) y < 0. Clearly insufficient.

(1)+(2) Now, remember that we can subtract inequalities with the signs in opposite direction --> subtract (2) from (1): $$z-y>0$$. So, we know that the second multiply in $$x(z-y)$$ is positive, but we still don't know the sign of $$x$$: from the stem ($$x>y$$) and the second statement ($$y<0$$) the only thing we can deduce is that $$x$$ is greater than negative number $$y$$, hence $$x$$ could be negative, positive or zero. Not sufficient.

Hope it's clear.
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Re: If x > y, is zx > yx? [#permalink]

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31 Jul 2012, 02:03
Its E.. bt i got c ..then i realized we must knw what wud be the value of x ..and value of x is not given ...so its E..
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Re: If x > y, is zx > yx? [#permalink]

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12 Dec 2013, 03:10
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Re: If x > y, is zx > yx? [#permalink]

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23 Dec 2013, 19:57
Does anyone have advice on how to tackle these problems faster? I always end up resorting to plugging in numbers and various conditions and even though that helps me ensure more accuracy, it usually takes me about 3 min. per such problem (inequalities with only variables).
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Re: If x > y, is zx > yx? [#permalink]

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07 Jul 2015, 09:51
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

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If x > y, is zx > yx? [#permalink]

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15 Sep 2015, 02:23
x>y and Is zx>yx? Y/N question

The question: Is z>x and x,y,z>0?

St.1 z>0. INSUFF (we do not know whether x,y>0)
St.2 y<0. INSUFF (we do not need other variables because if one is negative we cannot answer definitely)
St.1+St.2. Still y<0, so INSUFF

E
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If x > y, is zx > yx? [#permalink]

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24 Sep 2015, 11:19
just to make sure i understood it:
zx > yx --> we cannot simplify to z > y because we don't know if x is positive or negative, right?
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If x > y, is zx > yx? [#permalink]

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24 Sep 2015, 11:43
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nicksson wrote:
just to make sure i understood it:
zx > yx --> we cannot simplify to z > y because we don't know if x is positive or negative, right?

Yes exactly. In inequalities be very careful with cancelling variables without knowing for sure what signs are they.

In the current question, zx>xy --> x(z-y)>0

After combining the 2 statements, you do know that -y>0 and z>0 ---> z-y>0 but without knowing the sign of 'x', you will not be able to answer yes or no for the question asked.

Hope this helps.
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Re: If x > y, is zx > yx? [#permalink]

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20 Oct 2016, 04:19
Hello from the GMAT Club BumpBot!

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Re: If x > y, is zx > yx?   [#permalink] 20 Oct 2016, 04:19
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