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29 Nov 2009, 16:13
Kudos
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C
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Difficulty:
35%
(medium)
Question Stats:
64% (00:50) correct
36%
(01:13)
wrong
based on 28
sessions
History
Date
Time
Result
Not Attempted Yet
What is the value of x?
(1) 6x = √(3x)
(2) x > 0
(1) 6x = √(3x)
(2) x > 0
Archived Topic
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This topic has been closed and archived due to inactivity or violation of community quality standards. No more replies are possible here.
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29 Nov 2009, 16:23
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Pedros
(1) Square both sides --> \(36x^2=3x\) --> \(12x^2=x\), NOTE that here we can not reduce by \(x\), as we don't know the value of \(x\). Meaning that \(x\) can be zero and if so we can not reduce (divide) by zero --> \(x(12x-1)=0\) --> \(x=0\) OR \(x=\frac{1}{12}\). Two possible values for \(x\), not sufficient.
(2) \(x>0\), clearly not sufficient.
(1)+(2) \(x=0\) OR \(x=\frac{1}{12}\) BUT \(x>0\), \(x\) can not be zero, so \(x=\frac{1}{12}\). Sufficient.
Answer: C.
GROUND RULE:
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 can not divide by zero.
Never multiply (or reduce) inequality by variable (or expression with variable) if you don't know the sign of it or are not certain that variable (or expression with variable) doesn't equal to zero.
Archived Topic
Hi there,
This topic has been closed and archived due to inactivity or violation of community quality standards. No more replies are possible here.
Where to now? Join ongoing discussions on thousands of quality questions in our Data Sufficiency (DS) Forum
Still interested in this question? Check out the "Best Topics" block above for a better discussion on this exact question, as well as several more related questions.
Thank you for understanding, and happy exploring!
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