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Manager  Joined: 27 Feb 2010
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Location: Denver
Is |k| = 2? (1) k^2 = 4 (2) k = |-2|  [#permalink]

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4
6 00:00

Difficulty:   5% (low)

Question Stats: 77% (00:35) correct 23% (00:42) wrong based on 401 sessions

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Is |k| = 2?

(1) k^2 = 4
(2) k = |-2|
Math Expert V
Joined: 02 Sep 2009
Posts: 58417
Is |k| = 2? (1) k^2 = 4 (2) k = |-2|  [#permalink]

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Is |k| = 2?

(1) k^2 = 4 --> |k| = 2. Sufficient.

(2) k = |-2| --> k=2 --> |k| = 2. Sufficient.

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Math Revolution GMAT Instructor V
Joined: 16 Aug 2015
Posts: 8009
GMAT 1: 760 Q51 V42 GPA: 3.82
Re: Is |k| = 2? (1) k^2 = 4 (2) k = |-2|  [#permalink]

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Forget conventional ways of solving math questions. In DS, Variable approach is the easiest and quickest way to find the answer without actually solving the problem. Remember equal number of variables and independent equations ensures a solution.

Is |k| = 2?

(1) k^2 = 4
(2) k = |-2|

In the original condition, there is 1 variable(k), which should match with the number of equations. So you need 1 equation.
For 1) 1 equation, for 2) 1 equation, which is likely to make D the answer.
For 1), k=-2,2 but |k|=|2|,|-2|=2, which is unique and sufficient.
For 2), k=|-2|=2, which is unique and sufficient.
Therefore, the answer is D.

 For cases where we need 1 more equation, such as original conditions with “1 variable”, or “2 variables and 1 equation”, or “3 variables and 2 equations”, we have 1 equation each in both 1) and 2). Therefore, there is 59 % chance that D is the answer, while A or B has 38% chance and C or E has 3% chance. Since D is most likely to be the answer using 1) and 2) separately according to DS definition. Obviously there may be cases where the answer is A, B, C or E.
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Is |k| = 2? (1) k^2 = 4 (2) k = |-2|  [#permalink]

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Bunuel wrote:

Is |k| = 2?

(1) k^2 = 4 --> |k| = 2. Sufficient.

(2) k = |-2| --> k=2 --> |k| = 2. Sufficient.

Hello Bunuel,

I am not getting how option 2 is sufficient. As per question statement- $$|K| =2$$ so K can 2 or -2

Option 2 says K= |-2| =2, it doesn't give option of -2.
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Joined: 02 Sep 2009
Posts: 58417
Re: Is |k| = 2? (1) k^2 = 4 (2) k = |-2|  [#permalink]

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ammuseeru wrote:
Bunuel wrote:
Is |k| = 2?[/b]

(1) k^2 = 4 --> |k| = 2. Sufficient.

(2) k = |-2| --> k=2 --> |k| = 2. Sufficient.

Hello Bunuel,

I am not getting how option 2 is sufficient. As per question statement- $$|K| =2$$ so K can 2 or -2

Option 2 says K= |-2| =2, it doesn't give option of -2.

The question asks: Is |k| = 2?

(2) says: k = 2. If k = 2, then |k| = 2.
_________________ Re: Is |k| = 2? (1) k^2 = 4 (2) k = |-2|   [#permalink] 31 Dec 2018, 01:55
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