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M28-05

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M28-05  [#permalink]

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New post 16 Sep 2014, 01:28
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A
B
C
D
E

Difficulty:

  35% (medium)

Question Stats:

58% (00:49) correct 42% (00:50) wrong based on 232 sessions

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Re: M28-05  [#permalink]

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New post 18 Oct 2015, 11:27
2
danjbon wrote:
I think this is a high-quality question and I agree with explanation. I'm confused as to why I cannot divide statement 1 by zero to get to y=1. I know that x=0 is clearly a possibility i just don't get why I cannot divide both sides by X.


If you divide (reduce) xy = x by x, you assume, with no ground for it, that x does not equal to zero thus exclude a possible solution.

Never reduce equation by variable (or expression with variable), if you are not certain that variable (or expression with variable) doesn't equal to zero. We cannot divide by zero.
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Re M28-05  [#permalink]

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New post 16 Sep 2014, 01:28
Official Solution:


(1) \(xy = x\). Re-arrange and factor out \(x\) to get \(x(y-1)=0\). So, either \(x=0\) (and \(y\) can take any value) OR \(y=1\) (and \(x\) can take any value). Not sufficient.

(2) \(x+y=x\). This statemnt implies that \(y=0\). Not sufficient to answer whether \(x=0\).

(1)+(2) As from (2) \(y=0\neq{1}\) then according to (1) \(x=0\). Sufficient.


Answer: C
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Re M28-05  [#permalink]

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New post 17 Oct 2015, 14:04
I think this is a high-quality question and I agree with explanation. I'm confused as to why I cannot divide statement 1 by zero to get to y=1. I know that x=0 is clearly a possibility i just don't get why I cannot divide both sides by X.
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Re: M28-05  [#permalink]

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New post 03 Dec 2016, 20:41
why we cannot have a situation where both x and y are zero??it satisfies both the equations..and it has not been explicitly mentioned x and y are different??
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New post 05 Dec 2016, 02:00
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Re: M28-05  [#permalink]

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New post 15 Oct 2018, 11:13
What if x = 0 and y = 1 or y = 0 and x = 1
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New post 15 Oct 2018, 21:05
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Re: M28-05   [#permalink] 15 Oct 2018, 21:05
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