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Source: — Data Sufficiency |

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by Brent@GMATPrepNow » Mon Feb 23, 2009 4:42 pm
The question "Is 1/k > 0" can be rewritten as "is k positive?" since the only way for 1/k to be greater than 0 is for k to be positive.

(1) If 1/(k-1) is positive, then k-1 is positive: 0<k-1
Add 1 to both sides: 1<k
k is definitely positive
SUFF

(2) If 1/(k+1) is positive, then k+1 is positive: 0<k+1
Subtract 1 from both sides: -1<k
k can be either positive or negative.
INSUFF

The answer is A
Last edited by Brent@GMATPrepNow on Mon Feb 23, 2009 8:11 pm, edited 2 times in total.
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by welcome » Mon Feb 23, 2009 6:25 pm
same as Brent , I'll go for A. what is OA.
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Re: Value of K

by x2suresh » Mon Feb 23, 2009 7:57 pm
Agree with Brent A.
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by fighting_cax » Thu Feb 26, 2009 2:35 pm
Thanks Brent - your explanation is very clear.
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by Uri » Thu Feb 26, 2009 3:57 pm
Brent Hanneson wrote: (2) If 1/(k+1) is positive, then k+1 is positive: 0<k+1
Subtract 1 from both sides: -1<k
k can be either positive or negative.
INSUFF

The answer is A

From (2), we know that k>-1. And we are told explicitly that k is not 0, 1 or -1. Thus combining this two, k>1. Hence (2) should also be sufficient.

Please rectify me if I have made any mistake.
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by rolrol19 » Sun Mar 01, 2009 2:00 pm
Agree with Uri!
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by cramya » Sun Mar 01, 2009 3:39 pm
From (2), we know that k>-1. And we are told explicitly that k is not 0, 1 or -1. Thus combining this two, k>1. Hence (2) should also be sufficient.

Please rectify me if I have made any mistake
Agree with Uri!
A common mistake is to assume k is an integer. The problem states k is not 0,1 or -1 so it can be anything else(integer or fraction)


Stmt II

1/k+1 > 0

k= - 1/2 still 1/k+1 > 0 and 1/k is not greater than 0



Hope this helps!

Regards,
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by Uri » Mon Mar 02, 2009 1:41 pm
thanks, cramya! understood my mistake
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