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swati.sug
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 Posted: Mon Jul 14, 2008 2:40 pm Post subject: Please tell the flaw in my logic. Q 145 OG 11 ...Plz help |
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Is 1/p >r/(r^2 +2)
1. p = r
2.r > 0
Plz help..
Let me know what am I doing wrong if I solve it as below:
Cross multiplying the ques stem:
r^2 + 2 > pr
Is r^2 -pr +2 >0 ...This is what is asked..
Considering statement 1. p = r
Substituting in r^2 -pr + 2 > 0,
First two terms will cancel out regardless of whether both p and q are posiive or negative.
and remaining 2 > 0 is definatilely true.
So I selected OA) AStatement 1 is sufficent.
Please tell flaw in my logic. |
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Ian Stewart
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| Posted: Mon Jul 14, 2008 4:24 pm Post subject: Re: Please tell the flaw in my logic. Q 145 OG 11 ...Plz h |
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| swati.sug wrote: | Is 1/p >r/(r^2 +2)
1. p = r
2.r > 0
Plz help..
Let me know what am I doing wrong if I solve it as below:
Cross multiplying the ques stem:
r^2 + 2 > pr
Is r^2 -pr +2 >0 ...This is what is asked..
Considering statement 1. p = r
Substituting in r^2 -pr + 2 > 0,
First two terms will cancel out regardless of whether both p and q are posiive or negative.
and remaining 2 > 0 is definatilely true.
So I selected OA) AStatement 1 is sufficent.
Please tell flaw in my logic. |
I've highlighted above the mistake. You can't cross multiply here unless you know whether p is positive or negative; if p is negative, you would need to reverse the inequality.
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swati.sug
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| Posted: Tue Jul 15, 2008 7:46 am Post subject: |
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Thanks Ian
So what is the rights method to solve it.
Is it reversing the sign of the inequality when I consider the negative value(after cross mutiplying and simplifying).
Please illustrate .. |
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sm612
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| Posted: Tue Jul 15, 2008 8:24 am Post subject: |
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Apart from +ve, -ve values, (1) does not tell if r=0.
If this is the case then, we cannot find the result.
Combining 1 and 2 we can tell the answer. So C should be the answer.
What is OA? |
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