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Confusion

by [email protected] » Thu May 08, 2014 7:40 pm
Hi,
While reading a post from BTG, I realised that sqrt(x)=mod(x).
That means, Sqrt(16)=mod(4)=4, or sqrt(16)=4(always).
However, while solving an Q from Power Prep,I encountered an Q in which sqrt(16)=4 or -4.
PLEASE HELP

Reagrds,
Mukherjee
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by GMATGuruNY » Thu May 08, 2014 8:17 pm
[email protected] wrote:Hi,
While reading a post from BTG, I realised that sqrt(x)=mod(x).
That means, Sqrt(16)=mod(4)=4, or sqrt(16)=4(always).
However, while solving an Q from Power Prep,I encountered an Q in which sqrt(16)=4 or -4.
PLEASE HELP

Reagrds,
Mukherjee
Please post a screen shot of the question.
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by [email protected] » Thu May 08, 2014 8:19 pm
Hi mukherjee.tanuj3,

When dealing with these specific math issues, you have to pay careful attention to what you're given to start with.

IF you're given X^2 = 16, then there are 2 answers: 4 and -4

IF you're given Sqrt(16), then there's just 1 answer: 4

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by [email protected] » Thu May 08, 2014 9:46 pm
Hey GMATguruNY and Rich,
According to the post that I read in BTG, answer to the following Q must be D.
As, y^2=9 or x=y^2=9 or sqrt(x)=mod(3)=3(NOT -3).

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Please HELP. I'm LOST.

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Mukherjee
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by theCodeToGMAT » Thu May 08, 2014 10:13 pm
[email protected] wrote:Hey GMATguruNY and Rich,
According to the post that I read in BTG, answer to the following Q must be D.
As, y^2=9 or x=y^2=9 or sqrt(x)=mod(3)=3(NOT -3).

Image

Please HELP. I'm LOST.

Regards,
Mukherjee
Mukherjee, {D} cannot be answer. What is the source of the question?

sqrt(A) ==> +A
But, A^2 ==>4 ==> A can be 2 or -2
--------------

x + 2y + 1 = y - x
==> 2x + y = -1

To find: "x"

Statement 1:
y^2 = 9 ===> y can be 3 or -3
If "3" ==> 2x + 3 = -1 ==> x = -2
If "-3" ==> 2x - 3 = -1 ==> x = 1
INSUFFICIENT

Statement 2:
y = 3
SUFFICIENT

[spoiler]{B}[/spoiler]
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by [email protected] » Fri May 09, 2014 12:05 am
Hi mukherjee.tanuj3,

Rahul's explanation is correct. The answer is B, not D. Perhaps the original question has a typo in the explanation? If it's not a typo, then whoever wrote this question made an error in its construction.

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by [email protected] » Fri May 09, 2014 12:23 am
Thank You!
I understood my mistake.
OA B
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