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[DS]If a, b, and c are integers and abc ≠ 0

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anilbhat85
 Post subject: [DS]If a, b, and c are integers and abc ≠ 0
 Post Posted: Thu Aug 18, 2011 10:26 am 
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Students


Posts: 1
If a, b, and c are integers and abc ≠ 0, is a2 – b2 a multiple of 4?

(1) a = (c – 1)2

(2) b = c2 – 1


I have read the explanation. By i approached this problem by putting values for c

For c = 0 and 1 i got a^2-b^2 as 0. Should we consider o as a multiple of 4 ?

0*4 = 0 ?
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mithunsam
 Post subject: Re: [DS]If a, b, and c are integers and abc ≠ 0
 Post Posted: Thu Aug 18, 2011 11:59 am 
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Course Students


Posts: 76
The fact is that you cannot pick 0 or 1 for c.

Question states abc≠ 0. We cannot ignore this statement.

If c is 0, then abc will become 0.

If c is 1, then
stmt 1 => a = 0. Which means abc = 0
stmt 2 => b = 0. Which again means abc = 0

That means, c cannot be either 0 or 1.
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tim
 Post subject: Re: [DS]If a, b, and c are integers and abc ≠ 0
 Post Posted: Sat Sep 17, 2011 1:22 am 
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ManhattanGMAT Staff


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Location: Southwest Airlines, seat 21C
good point about c not being 0. nevertheless, 0 is indeed a multiple of 4. it is a multiple of every integer, in fact..

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Tim Sanders
Manhattan GMAT Instructor
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yousuf_azim
 Post subject: Re: [DS]If a, b, and c are integers and abc ≠ 0
 Post Posted: Thu Sep 29, 2011 10:37 am 
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Students


Posts: 45
What is the ANS?
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jnelson0612
 Post subject: Re: [DS]If a, b, and c are integers and abc ≠ 0
 Post Posted: Sun Nov 13, 2011 11:28 pm 
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ManhattanGMAT Staff


Posts: 1857
yousuf_azim wrote:
What is the ANS?


The answer is C.

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Jamie Nelson
ManhattanGMAT Instructor
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