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Re: If x y and z are positive is xz = 7xy ?
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27 Oct 2014, 02:33
If x y and z are positive is xz = 7xy ?
(1) z/y = 7 --> z = 7y. Substitute the value of z in the question: is x(7y) = 7xy. Since LHS and RHS are the same then the answer to the question is YES. Sufficient.
(2) x/y = 1 --> x = y. Substitute the value of y in the question: is xz = 7x^2 ? --> is z = 7x ? Since we cannot answer this question neither with a definite YES nor with a definite NO, the statements is not sufficient.
Re: If x y and z are positive is xz = 7xy ?
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11 Dec 2014, 02:17
My approach (generally speaking)
Whenever we see common terms on LHS & RHS even if they are +ve we shouldn't be in a hurry to cancel them. Set up the equation first.
xz=7xy x(z-7y)=0 so solution is either x=0 or z=7y so from statement 1 we get z=7y. so sufficient from statement 2 we don't get anything. Insufficient.
The essence in these equations/inequalities is to know the solution set and work around/from that. my 2 cents.
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Re: If x y and z are positive is xz = 7xy ?
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10 Apr 2016, 20:45
Bunuel wrote:
If x y and z are positive is xz = 7xy ?
(1) z/y = 7 --> z = 7y. Substitute the value of z in the question: is x(7y) = 7xy. Since LHS and RHS are the same then the answer to the question is YES. Sufficient.
(2) x/y = 1 --> x = y. Substitute the value of y in the question: is xz = 7x^2 ? --> is z = 7x ? Since we cannot answer this question neither with a definite YES nor with a definite NO, the statements is not sufficient.
Re: If x y and z are positive is xz = 7xy ?
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11 Apr 2016, 00:04
Alok322 wrote:
Bunuel wrote:
If x y and z are positive is xz = 7xy ?
(1) z/y = 7 --> z = 7y. Substitute the value of z in the question: is x(7y) = 7xy. Since LHS and RHS are the same then the answer to the question is YES. Sufficient.
(2) x/y = 1 --> x = y. Substitute the value of y in the question: is xz = 7x^2 ? --> is z = 7x ? Since we cannot answer this question neither with a definite YES nor with a definite NO, the statements is not sufficient.
Re: If x y and z are positive is xz = 7xy ?
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12 Aug 2016, 08:41
Neeraj91 wrote:
Hi all,
First post here. I have been lurking for a while, never had to post because the solutions were always great!
I am a bit stumped here in this question though. I know I'm doing something silly. If someone can please shed some light on what I'm doing wrong...
I chose D because, when you arrive at x = y, I just replaced x in the original stem by y. So I get zy=7y^2 and then on cancelling I come to z=7y.
Please help!
Please check here: if-x-y-and-z-are-positive-is-xz-7xy-187488.html#p1433632 When you substitute x with y in the question, the question becomes "is z = 7x ?" Since we cannot answer this question neither with a definite YES nor with a definite NO, the statements is not sufficient.
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Re: If x y and z are positive is xz = 7xy ?
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28 Sep 2017, 13:24
Top Contributor
davidfrank wrote:
If x y and z are positive is xz = 7xy ?
(1) z/y = 7 (2) x/y = 1
Target question:Is xz = 7xy ? This is a good candidate for rephrasing the target question.
Since we're told that x is positive, we can take the equation xz = 7xy and divide both sides by x to get an EQUIVALENT equation: z = 7y This allows us to REPHRASE the target question and ask an easier question.... REPHRASED target question:Is z = 7y ?
Statement 1: z/y = 7 Multiply both sides by y to get: z = 7y Perfect - the answer to our REPHRASED target question is "Yes, z DOES equal 7y" Since we can answer the REPHRASED target question with certainty, statement 1 is SUFFICIENT
Statement 2: x/y = 1 Keep in mind that our REPHRASED target question asks "Is z = 7y ?" Since statement 2 provides no information about z, we cannot determine whether or not z = 7y Since we cannot answer the REPHRASED target question with certainty, statement 2 is NOT SUFFICIENT
Re: If x y and z are positive is xz = 7xy ?
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26 Nov 2018, 00:49
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