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If x and y are non-zero integers

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hima.batavia
 Post subject: If x and y are non-zero integers
 Post Posted: Sat Nov 06, 2010 2:08 am 
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Course Students


Posts: 2
If x and y are non-zero integers and |x| + |y| = 32, what is xy?

(1) -4x – 12y = 0

(2) |x| – |y| = 16


I don't understand why you assume that x and y are opposite signs based on simplifying the first expression.

Thanks!
Hima
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jnelson0612
 Post subject: Re: If x and y are non-zero integers
 Post Posted: Sat Nov 06, 2010 9:26 pm 
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ManhattanGMAT Staff


Posts: 1857
Hi Hima,
Take a look at the first expression, statement 1. You have
-4x - 12y = 0.

If I add 12y to both sides, I get -4x = 12y. If I divide both sides by -4, I get x=-3y.

If x = -3y, then we have the following two scenarios. Either:
a) x is positive and y is negative
OR
b) x is negative and y is positive

Notice how it is impossible for both to be negative or positive.

I hope this helps!

_________________
Jamie Nelson
ManhattanGMAT Instructor
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hima.batavia
 Post subject: Re: If x and y are non-zero integers
 Post Posted: Mon Nov 29, 2010 2:19 am 
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Course Students


Posts: 2
Thanks Jamie!

I have a follow-up question. Why do you convert them back to absolute values? When do you use that technique as a general rule?

Cheers,
Hima
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jnelson0612
 Post subject: Re: If x and y are non-zero integers
 Post Posted: Mon Nov 29, 2010 3:13 pm 
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ManhattanGMAT Staff


Posts: 1857
hima.batavia wrote:
Thanks Jamie!

I have a follow-up question. Why do you convert them back to absolute values? When do you use that technique as a general rule?

Cheers,
Hima


Hi Hima,
Sorry, I'm not understanding your question "why do you convert them back to absolute values?" Can you elaborate?

Thank you!

_________________
Jamie Nelson
ManhattanGMAT Instructor
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rite2deepti
 Post subject: Re: If x and y are non-zero integers
 Post Posted: Wed Dec 01, 2010 10:40 am 
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Students


Posts: 3
jnelson0612 wrote:
hima.batavia wrote:
Thanks Jamie!

I have a follow-up question. Why do you convert them back to absolute values? When do you use that technique as a general rule?

Cheers,
Hima


Hi Hima,
Sorry, I'm not understanding your question "why do you convert them back to absolute values?" Can you elaborate?

Thank you!

What is the OA I am getting B as my answer
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jnelson0612
 Post subject: Re: If x and y are non-zero integers
 Post Posted: Fri Dec 03, 2010 2:35 am 
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ManhattanGMAT Staff


Posts: 1857
rite2deepti, the correct answer is A.

See this link to read the full explanation: cat-question-opposite-signs-t1514.html

Thank you,

_________________
Jamie Nelson
ManhattanGMAT Instructor
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