If k ≠0, 1 or -1, is 1 / k > 0?
1) 1 / k - 1 > 0
2) 1 / k + 1 > 0
OA: A
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A little help please
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Brent@GMATPrepNow
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This question would benefit from some parentheses.fambrini wrote:If k ≠0, 1 or -1, is 1 / k > 0?
1) 1 / k - 1 > 0
2) 1 / k + 1 > 0
OA: A
Does 1 / k - 1 mean 1/(k-1) or (1/k) - 1?
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GMATGuruNY
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In order for 1/k to be positive, k must be positive.fambrini wrote:If k ≠0, 1 or -1, is 1 / k > 0?
1) 1/(k-1) > 0
2) 1/(k+1) > 0
Question stem, rephrased:
Is k>0?
Statement 1:
In order for 1/(k-1) to be positive, k-1 must be positive:
k-1>0
k>1.
Thus, k>0.
SUFFICIENT.
Statement 2:
In order for 1/(k+1) to be positive, k+1 must be positive:
k+1>0
k>-1
If k=2, the answer to the question stem is YES.
If k=-1/2, the answer to the question stem is NO.
INSUFFICIENT.
The correct answer is A.
Last edited by GMATGuruNY on Sat Oct 22, 2016 7:56 am, edited 1 time in total.
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Mo2men
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HI Mitch,GMATGuruNY wrote:In order for 1/k to be positive, k must be positive.fambrini wrote:If k ≠0, 1 or -1, is 1 / k > 0?
1) 1/(k-1) > 0
2) 1/(k+1) > 0
Question stem, rephrased:
Is k>0?
Statement 1:
In order for 1/(k-1) to be positive, k-1 must be positive:
k-1>0
k>1.
Thus, k>0.
SUFFICIENT.
Statement 2:
In order for 1/(k+1) to be positive, k+1 must be positive:
k+1>0
k>-1
If k=1, the answer to the question stem is YES.
If k=-1/2, the answer to the question stem is NO.
INSUFFICIENT.
The correct answer is A.
As per the question stem, K CAN'T be 1.
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GMATGuruNY
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Good catch.Mo2men wrote:HI Mitch,
As per the question stem, K CAN'T be 1.
I've amended my post accordingly.
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Matt@VeritasPrep
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Mo2men
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Hi Mitch,GMATGuruNY wrote:In order for 1/k to be positive, k must be positive.fambrini wrote:If k ≠0, 1 or -1, is 1 / k > 0?
1) 1/(k-1) > 0
2) 1/(k+1) > 0
Question stem, rephrased:
Is k>0?
Statement 1:
In order for 1/(k-1) to be positive, k-1 must be positive:
k-1>0
k>1.
Thus, k>0.
SUFFICIENT.
Statement 2:
In order for 1/(k+1) to be positive, k+1 must be positive:
k+1>0
k>-1
If k=2, the answer to the question stem is YES.
If k=-1/2, the answer to the question stem is NO.
INSUFFICIENT.
The correct answer is A.
what would be the critical points in this problem?
In statement 1, I assume they are 0 & 1
In statement 2, they are -1 & 0
Do I miss anything?
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Matt@VeritasPrep
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You're probably fine just thinking of 1 in S1 and -1 in S2. (0 isn't as critical, since all that really matters is whether your denominator is + or -.)Mo2men wrote: In statement 1, I assume they are 0 & 1
In statement 2, they are -1 & 0
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Mo2men
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i agree with you but I though in 0 as stem ask for 1/k so 0 would be critical point. Also, it would help me in statement 2 to check points (such as -1/2) between -1 & 0. otherwise, I would check point such 2 as it is greater than -1.Matt@VeritasPrep wrote:You're probably fine just thinking of 1 in S1 and -1 in S2. (0 isn't as critical, since all that really matters is whether your denominator is + or -.)Mo2men wrote: In statement 1, I assume they are 0 & 1
In statement 2, they are -1 & 0
You may argue that I need to check negative fractions to ensure the validity of the statement. However, I find it easy to draw critical points on number line with those points and determine range.
