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Difficult Number Properties Question

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Difficult Number Properties Question

by skalevar » Fri Oct 15, 2010 2:07 pm
If x and y are integers and 2x-y =11, then 4x + y CANNOT Be?

A. -5
B. 1
C. 13
D. 17
E. 55


Where do you even begin with such a problem?

Thanks so much for your help!


(Source is Ready for GMAT.com Advanced Quant; no explanation provided.)
OA is D
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by uwhusky » Fri Oct 15, 2010 2:43 pm
I think the first step is always try to simplify the variables.

2x - y = 11, then 2x - 11 = y.

So 4x + 2x - 11 = 6x - 11.

So the question is asking, 11 + which of the options is divisible by 6.

A: 11 + (-5) = 6; yes.
B: 11 + 1 = 12; yes.
C: 11 + 13 = 24; yes.
D: 11 + 17 = 28; no.
E: 11 + 55 = 66; yes.

Answer is D.
Yep.
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by skalevar » Fri Oct 15, 2010 2:47 pm
thanks a lot! That really helps. It seems so easy once you get started....
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by diebeatsthegmat » Fri Oct 15, 2010 6:46 pm
skalevar wrote:If x and y are integers and 2x-y =11, then 4x + y CANNOT Be?

A. -5
B. 1
C. 13
D. 17
E. 55


Where do you even begin with such a problem?

Thanks so much for your help!


(Source is Ready for GMAT.com Advanced Quant; no explanation provided.)
OA is D
because 2x-y=11 (1) and 4x+y=a (2)
(1)+(2)=6x=11+a
we see that 6x=11+17=28 and 28 is cant : 6
thus answer is D
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