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GMAT Prep1 - Numbers

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GMAT Prep1 - Numbers

by fsutanto » Sun Sep 26, 2010 9:41 am
I had a closer look at the question and am still convinced that the answer should be (c).

According to GMAT, the correct answer is (a), statement I is sufficient. How is it sufficient? What if S lies to the left (i.e. negative number) of zero and T lies to the right (positive) of zero? This would make statement I insufficient to answer the question because "distance" by definition will always be a positive number. Statement II clarifies the issue by saying that S and T do not have the same sign.

Can anyone help me with the logic here?


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by tlt2372 » Sun Sep 26, 2010 10:20 am
fsutanto wrote:I had a closer look at the question and am still convinced that the answer should be (c).

According to GMAT, the correct answer is (a), statement I is sufficient. How is it sufficient? What if S lies to the left (i.e. negative number) of zero and T lies to the right (positive) of zero? This would make statement I insufficient to answer the question because "distance" by definition will always be a positive number. Statement II clarifies the issue by saying that S and T do not have the same sign.

Can anyone help me with the logic here?


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I thought the same thing at first. But then I read the question closer, s and t are two different numbers.

Statement 1 tells us that the numbers are the same distance from zero. THat tells me that they are the same number, but one is negative and one is positive.

So Statement 1 is suff
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by this_time_i_will » Sun Sep 26, 2010 10:27 am
I: since the distance b/w s and 0 is same as the distance b/w t and 0, we can have following two conditions:

condition a: ---(s)----------------0---------------(t)--- or -----(t)------------------0-----------------(s)-----
condition b: ---(s/t)--------------0------ or -------0-----------(s/t).... : that is point s and t are same.

But as given in the question, s and t are different and so condition b is ruled out.

now from condition a, for both cases, s-t = 0 and hence, A.
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by clock60 » Sun Sep 26, 2010 11:07 am
my two cents, although the problem is already elaborated
we are asked if s=-t,
(1) we are told that distance between s and 0 is the same as distance between 0 and t, this can be written in math terms
|0-s|=|t-0|, or |-s-0|=|t-0|. i think that here does not matter what signs have t or s as in any case we come to the case that |t|=|s|
from here t^2-s^2=(t-s)(t+s)=0, and it is possible if t=s, bot according to the problem t and s are different numbers thus t+s=0 or t=-s so sufficient
(2) insufficient no need to prove
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