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If (x/y)^(1/2)=n, what is the value of x?

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reddevil00
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If (x/y)^(1/2)=n, what is the value of x? [#permalink] New post   06 Apr 2012, 18:49
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If (x/y)^(1/2)=n, what is the value of x?

(1) (n^2)y = 100
(2) n= 5 and y = 4

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This question is from Total GMAT Math. The statement (1) provides that (n^2)y = 100 which implies that n(y^(1/2)) can be either 10 or -10. However, the solution provided by the book states that the above value is only 10. Hence I chose B, sine the statement (1) can be both 10 or -10. Is my approach incorrect?

The official answer is D.

Thanks in advance for your expertise!


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D
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Re: If (x/y)^(1/2)=n, what is the value of x? [#permalink] New post   06 Apr 2012, 21:09
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Rearranging/squaring the equation given in the question saves you from the troubles with square roots.

\(\sqrt{\frac{x}{y}}=n\)
\(\frac{x}{y}=n^2\)
\(x=(n^2)y\)

Statement 1: \((n^2)y=100\)
Hence statement 1 is sufficient.



Also if you were to continue from the equation you've arrived at,
When its 10:
\(n\sqrt{y}=10\)
\((n^2)y=10^2\)
\((n^2)y=100=x\)

When its -10:
\(n\sqrt{y}=-10\)
\((n^2)y=(-10)^2\)
\((n^2)y=100=x\)

Both lead to \(x=100\) so statement 1 is still sufficient.
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Re: If (x/y)^(1/2)=n, what is the value of x? [#permalink] New post   07 Apr 2012, 02:06
andrewh wrote:
1) (n^2)y = 100
2) n= 5 and y = 4

This question is from Total GMAT Math. The statement (1) provides that (n^2)y = 100 which implies that n(y^(1/2)) can be either 10 or -10. However, the solution provided by the book states that the above value is only 10. Hence I chose B, sine the statement (1) can be both 10 or -10. Is my approach incorrect?

The official answer is D.

Thanks in advance for your expertise!



Given that
(x/y)power(1/2) = n
x/y = n square
x = y. n square


now,

1. y.nsquare = 100
sufficient

2. values for Y and N are given, then this is sufficient too...

so my ANSWER is D
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Re: If (x/y)^(1/2)=n, what is the value of x? [#permalink] New post   07 Apr 2012, 09:01
Thanks so much. I can believe I didn't see that :(.
Thanks again for your support!
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Re: If (x/y)^(1/2)=n, what is the value of x? [#permalink] New post   23 May 2013, 06:37
reddevil00 wrote:
If (x/y)^(1/2)=n, what is the value of x?

(1) (n^2)y = 100
(2) n= 5 and y = 4

This question is from Total GMAT Math. The statement (1) provides that (n^2)y = 100 which implies that n(y^(1/2)) can be either 10 or -10. However, the solution provided by the book states that the above value is only 10. Hence I chose B, sine the statement (1) can be both 10 or -10. Is my approach incorrect?

The official answer is D.

Thanks in advance for your expertise!



yes, what u have misses is : l x l is +/- and again the same way x^2 is always positive but a root need not be, here we have square only dude.
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Re: If (x/y)^(1/2)=n, what is the value of x? [#permalink] New post   24 Dec 2016, 09:34
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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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Re: If (x/y)^(1/2)=n, what is the value of x? [#permalink]
24 Dec 2016, 09:34
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