DS

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Source: — Data Sufficiency |

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by DanaJ » Wed Jan 21, 2009 11:03 am
IMO A would be the correct answer. If you have p = r, then your equation will be 1/r > r(r^2 +2). That means that r^2 + 2 > r^2, which is always true, since r^2 will always be positive. It's like saying that 2 > 0, which is always true.
B is not sufficient, since r/(r^2 + 2) is always greater than 0 (given that r and r^2+2 are always positive), while 1/p could be negative, if p is negative.

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by maihuna » Wed Jan 21, 2009 11:18 am
DanaJ wrote:IMO A would be the correct answer. If you have p = r, then your equation will be 1/r > r(r^2 +2). That means that r^2 + 2 > r^2, which is always true, since r^2 will always be positive. It's like saying that 2 > 0, which is always true.
B is not sufficient, since r/(r^2 + 2) is always greater than 0 (given that r and r^2+2 are always positive), while 1/p could be negative, if p is negative.
DanaJ, but w/o knowing the sign of r u cant cross multiply right?

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by DanaJ » Wed Jan 21, 2009 11:26 am
Yep, thank you for noticing that.... Sorry... Then I guess it takes both stmts to solve this.