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bhumit920
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Post subject: GMAT Question Bank Problem  Posted: Sun Sep 19, 2010 4:49 pm |
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I really can't crack this one; any help would be really appreciated.
If q, r, and s are consecutive even integers and q < r < s, which of the following CANNOT be the value of s2 – r2 – q2?
A. -20
B. 0
C. 8
D. 12
E. 16
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gagandeepm
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Post subject: Re: GMAT Question Bank Problem Posted: Sun Sep 19, 2010 10:25 pm |
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Assume the even numbers to be 2n+4(s), 2n+2(r), 2n(q).
solving for s2-q2-r2 = 12 - 4n(n-2)
Now check for the choice a to e which will not yield a integer value for n.
Except C all other yield a integer value of n.
So the right answer is C
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tim
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Post subject: Re: GMAT Question Bank Problem Posted: Mon Sep 20, 2010 8:17 pm |
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Location: Southwest Airlines, seat 21C
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thanks; this is a great explanation. however, bhumit, this is very close to the answer given in our materials, so can you let us know whether this was an adequate explanation?
_________________
Tim Sanders
Manhattan GMAT Instructor
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dibrushi
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Post subject: Re: GMAT Question Bank Problem Posted: Tue Aug 09, 2011 1:28 pm |
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Hi! What about n=0??We can not have n zero, can't we??so shouldn't it be 12?
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tim
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Post subject: Re: GMAT Question Bank Problem Posted: Fri Aug 12, 2011 11:27 pm |
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why is n not supposed to be 0?
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Tim Sanders
Manhattan GMAT Instructor
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mmsmoney
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Post subject: Re: GMAT Question Bank Problem Posted: Fri Dec 30, 2011 3:51 am |
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The ans is A
Substitute the foll examples for the three integers
2 4 6 - will give 0
-2 -4 -6 - will give 16
2 0 -2 - will give 8
0 -2 -4 - will give 12
you cant get a negative value at all thats the trick
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tim
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Post subject: Re: GMAT Question Bank Problem Posted: Sat Dec 31, 2011 1:44 pm |
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Location: Southwest Airlines, seat 21C
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You’re not substituting correctly. Try again..
_________________
Tim Sanders
Manhattan GMAT Instructor
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mmsmoney
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Post subject: Re: GMAT Question Bank Problem Posted: Sat Dec 31, 2011 4:25 pm |
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oh am sorry Mr Tim i thought it was 2 multiplied by s...
didn't notice it as a "square"...
anyway am wrong, if it was multiplied by 2 all options are possible..
its better if u remove that post so others wont be confused...
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jnelson0612
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Post subject: Re: GMAT Question Bank Problem Posted: Tue Jan 10, 2012 11:28 am |
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mmsmoney wrote: oh am sorry Mr Tim i thought it was 2 multiplied by s...
didn't notice it as a "square"...
anyway am wrong, if it was multiplied by 2 all options are possible..
its better if u remove that post so others wont be confused... No worries! Other students will learn from your error. Glad you caught it!
_________________
Jamie Nelson
ManhattanGMAT Instructor
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