GMAT Prep data sufficiency question - tricky?

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A number line is shown in the question.

r s t


r, s and t are in the number line as shown above.
r is to the left of s and s is to the left of t.

On the number line shown above, is zero halfway between r and s?

1. s is to the right of zero.
2. The distance between t and r is same as the distance between t and -s.

Please move your mouse over the darkened spot below to view the answer.

I chose B

But the correct answer is C.

With statement 2, we can infer that r = -s, because r is to the left of s in the number line. So s can not be negative. If s were negative, r would be to the right of s. So, zero should be halfway between r and s. Case closed.

Your explanation is much appreciated.
Thanks
Paddy
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by cubicle_bound_misfit » Fri Jun 27, 2008 12:37 pm
Hi Paddy,

you did almost correct only made the mistake of taking stmt 1 into account while considering stmt 2.

Let's conside the scenario when we take both the stmt together.

S is positive and r is left to it. now -s will be negative no.

as r is left to t also if the distance between r-t and r-(-s) is same -s and t has to be the same point

or r =-s hence SUFF

ans C.

regards,
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by arvindm07 » Fri Jun 27, 2008 4:58 pm
even i do not understand how could it be C. B is enough coz, no matter what number (positive or -ve) t-r = t-(-s) i.e. t-r = t+s which makes it s = -r which makes 0 to be in the middle of r and s.
I don't see how can the answer be C. If anyone can think of something i am missing, please help.

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by Ian Stewart » Fri Jun 27, 2008 6:01 pm
For online GMAT math tutoring, or to buy my higher-level Quant books and problem sets, contact me at ianstewartgmat at gmail.com

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by arvindm07 » Fri Jun 27, 2008 6:26 pm
Thanks for the explanation, i didn't work with all the numbers on the negative side, just tried it with one of two numbers ( -9, -8, -1) and concluded it was not possible.
Thanks again.