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# If k is not 0,1,-1, is 1/k >0? 1. 1/k-1 >0 2. 1/k+1

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Manager
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If k is not 0,1,-1, is 1/k >0? 1. 1/k-1 >0 2. 1/k+1 [#permalink]

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09 Apr 2006, 04:30
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If k is not 0,1,-1, is 1/k >0?

1. 1/(k-1) >0

2. 1/(k+1) >0

OPEN DISCUSSION OF THIS QUESTION IS HERE: if-k-does-not-equal-0-1-or-1-is-1-k-0-1-1-k-119545.html
[Reveal] Spoiler: OA

Last edited by Bunuel on 08 Aug 2012, 05:03, edited 1 time in total.
Edited the question and added the OA.

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09 Apr 2006, 05:39
jodeci wrote:
If k is not 0,1,-1, is 1/k >0?

1. 1/k-1 >0

2. 1/k+1 >0

1/ (k-1) > 0 --> k-1> 0 because 1> 0 --> k>1 --> k>0 --> 1/k> 0
-->suff

2/ 1/ ( k+1) > 0 --> k+1> 0 becoz 1> 0 --> k> -1
We don't know if k> 0 ---> impossible to conclude whether 1/k> 0 --> insuff

A it is.

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Manager
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04 Jun 2006, 00:54
if k is not equal to 0,1, or -1 , is k>0?
1. 1/(k-1)>0
2.1/(k+1)>0

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Manager
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Re: GMATPREP : ds k [#permalink]

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04 Jun 2006, 03:12
dinesh8 wrote:
if k is not equal to 0,1, or -1 , is k>0?
1. 1/(k-1)>0
2.1/(k+1)>0

A

statement 2 allows numbers between -1 to 0 aswell

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Manager
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Re: GMATPREP : ds k [#permalink]

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04 Jun 2006, 10:55
shobhitb wrote:
dinesh8 wrote:
if k is not equal to 0,1, or -1 , is k>0?
1. 1/(k-1)>0
2.1/(k+1)>0

A

statement 2 allows numbers between -1 to 0 aswell

Can you please explain how you came to A?

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VP
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Re: GMATPREP : ds k [#permalink]

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04 Jun 2006, 11:18
dinesh8 wrote:
if k is not equal to 0,1, or -1 , is k>0?
1. 1/(k-1)>0
2.1/(k+1)>0

(i) 1/(k-1)>0
it has two inequalities: either 1>k-1 or 1<k-1
if 1>k-1, 2>k>1.
if 1<k-1, 2<k. so k must be >1.

2.1/(k+1)>0
1>(k+1)
0>k.

1<(k+1)
k<0. so not enough.........

A.

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DS - positive or negative [#permalink]

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21 Nov 2007, 07:59
If K is not equal to 0, 1, -1, is 1/k >0?

(1) 1/(k-1) >0

(2) 1/(k+1) >0

I chose D, but the OA is A.
In statement 1, the only way it can be positive is to have K greater than or equal to 2, which subsequently 1/k will always be positive.
As for statement 2, the only way it can be positive is also by using a number either greater than or equal to 2 in order to end up with 1/k as positive, yet according to the OA, statement 2 is not suff. can someone explain to me how?
thanks

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Manager
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Re: DS - positive or negative [#permalink]

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21 Nov 2007, 08:03
tarek99 wrote:
If K is not equal to 0, 1, -1, is 1/k >0?

(1) 1/(k-1) >0

(2) 1/(k+1) >0

I chose D, but the OA is A.
In statement 1, the only way it can be positive is to have K greater than or equal to 2, which subsequently 1/k will always be positive.
As for statement 2, the only way it can be positive is also by using a number either greater than or equal to 2 in order to end up with 1/k as positive, yet according to the OA, statement 2 is not suff. can someone explain to me how?
thanks

I got A.

Statement 2 works if say, x = -0.9 as it would read - 1/0.1 >0
However, 1/-0.9 < 0

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CEO
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21 Nov 2007, 08:18
look at attached drawing.
Attachments

GC55958.gif [ 8.55 KiB | Viewed 3202 times ]

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SVP
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21 Nov 2007, 10:49
ok i get it. so you always have to consider the decimals whenever the question doesn't specify that they are integers in the first place.

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Intern
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denominator gets larger / smaller [#permalink]

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25 Nov 2007, 20:47
if k is not = 0, 1 or -1, is 1/k>0?

1) 1/k-1 >0
2) 1/k+1 >0

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CEO
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Schools: Chicago (Booth) - Class of 2011
GMAT 1: 750 Q50 V40

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25 Nov 2007, 23:25
does "1/k-1" mean "(1/k)-1" or "1/(k-1)"? Please, write unambiguously

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Re: denominator gets larger / smaller [#permalink]

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26 Nov 2007, 00:44
jenniferia2002 wrote:
if k is not = 0, 1 or -1, is 1/k>0?

1) 1/k-1 >0
2) 1/k+1 >0

I believe the answer is A.

Im not sure though b/c i dunno if am reading the problem right. agree w/ walker, us paranthesis plz.

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26 Nov 2007, 01:11
if k is not = 0, 1 or -1, is 1/k>0?

1) 1/k-1 >0
2) 1/k+1 >0

question ask if K is +ve?

from 1

k-1>0 ie> k>1..................suff

from2

k+1>0 ie k>-1 , k is not a must an intiger so it could be = -1/2 or it could be 3 ...insuff

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Director
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14 Apr 2008, 23:23
If K is not equal to 0,1,-1, is $$1/k > 0$$?

( i ) $$1/(k-1)>0$$

( ii ) $$1/(k+1)>0$$

Last edited by LM on 15 Apr 2008, 00:08, edited 1 time in total.

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Senior Manager
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14 Apr 2008, 23:29
A, as statement b fails when k=-0.5 or any other decimal lower than 1.

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14 Apr 2008, 23:50
dushver wrote:
A, as statement b fails when k=-0.5 or any other decimal lower than 1.

Did you plug in the different values of "K" or did you solve the inequality in general? Could you please elaborate on logical approach?

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15 Apr 2008, 19:38
LM wrote:
dushver wrote:
A, as statement b fails when k=-0.5 or any other decimal lower than 1.

Did you plug in the different values of "K" or did you solve the inequality in general? Could you please elaborate on logical approach?

LM wrote:
If K is not equal to 0,1,-1, is $$1/k > 0$$?

( i ) $$1/(k-1)>0$$

( ii ) $$1/(k+1)>0$$

A
My reasoning:
the question is similar to k>0?, and keep the condition of k in mind. Go
1, 1/(k-1) >0, again similar to k-1 >0, so k>1, not only satify the conditions but also answer the question. Sufficient
2. again: k+1>0, so k>-1. Stop and think a little. Although combined with the conditions " k is not equal 0, 1, even -1, it still not enought to answer the question. k still can be equal to any fraction running from -1 to 0. Right?
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15 Apr 2008, 21:33
LM wrote:
If K is not equal to 0,1,-1, is $$1/k > 0$$?

( i ) $$1/(k-1)>0$$

( ii ) $$1/(k+1)>0$$

A.

1. k is not -ve. so suff.
2. k could be -ve. nsf
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11 Aug 2009, 08:07
If k is not equal to 0,1 or -1......Is 1/k >0??

1) 1/(k-1) >0

2) 1/(k+1) >0

Kudos [?]: 34 [0], given: 9

k#0,1,-1   [#permalink] 11 Aug 2009, 08:07

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