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What is the value of k ? (1) k*|k| = 4 (2) |k|*|k| = 4

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Bunuel
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What is the value of k ? (1) k*|k| = 4 (2) |k|*|k| = 4 [#permalink] New post   29 Nov 2018, 02:16
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What is the value of k ?

(1) k*|k| = 4
(2) |k|*|k| = 4


M36-29

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Bunuel
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Re: What is the value of k ? (1) k*|k| = 4 (2) |k|*|k| = 4 [#permalink] New post   11 Oct 2021, 09:01
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Bunuel wrote:
What is the value of k ?

(1) k*|k| = 4
(2) |k|*|k| = 4


M36-29


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What is the value of k ?

(1) \(k*|k| = 4\)

Notice that \(k\) cannot be negative because in this case \(k*|k| = (negative)(positive)=negative \neq 4\). So, \(k\) must be positive. In this case, \(|k|=k\) and we'd have \(k*k=4\), which gives \(k=2\) (remember \(k\) is positive so cannot be -2). Sufficient.

(2) \(|k|*|k| = 4\)

\(|k|^2 = 4\);

\(|k|= 2\);

\(k= 2\) or \(k=-2\). Not sufficient.


Answer: A
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Re: What is the value of k ? (1) k*|k| = 4 (2) |k|*|k| = 4 [#permalink] New post   29 Nov 2018, 02:35
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Bunuel wrote:
What is the value of k ?

(1) k*|k| = 4
(2) |k|*|k| = 4


Since our expressions are both similar to k^2 = 4, we'll guess that the two possible options are 2 or -2.
Then all we need to do is check these two numbers, an Alternative approach.

(1) 2*|2| = 4 so k = 2 works. (-2)*|(-2)| = -4 so k = -2 does not work. Since no other number gives k^2 = 4, then k must be equal to 2.
Sufficient.

(2) |2|*|2|=4 so k = 2 works. |(-2)|*|(-2)| = 4 so k = -2 also works.
Insufficient.

(A) is our answer
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Re: What is the value of k ? (1) k*|k| = 4 (2) |k|*|k| = 4 [#permalink] New post   29 Nov 2018, 04:06
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Bunuel wrote:
What is the value of k ?

(1) k*|k| = 4
(2) |k|*|k| = 4



from 1 : value of k would be +2

sufficeint
from2 K can be +/-2 so insufficient..
IMO A is correct..
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Re: What is the value of k ? (1) k*|k| = 4 (2) |k|*|k| = 4 [#permalink] New post   29 Nov 2018, 05:40
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Bunuel wrote:
What is the value of k ?

(1) k*|k| = 4
(2) |k|*|k| = 4



Statement 1: |k| = positive. k has to be positive in that case. 2*2 = 4. k=2.

Statement 2: |k|*|k| = 4. Now this is a bit complicated. |k| is a modulus . k can be negative or positive . NOT sufficient.

The best answer is A.
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Re: What is the value of k ? (1) k*|k| = 4 (2) |k|*|k| = 4 [#permalink] New post   29 Nov 2018, 13:04
Bunuel wrote:
What is the value of k ?

(1) k*|k| = 4
(2) |k|*|k| = 4


S1) k * a positive value = positive number -> k must be positive. Need the positive solution to k^2 = 4. k = 2. SUFFICIENT
S2) k=2 or k=-2 are solutions. INSUFFICIENT

Answer A
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Re: What is the value of k ? (1) k*|k| = 4 (2) |k|*|k| = 4 [#permalink] New post   24 Dec 2018, 01:33
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Bunuel wrote:
What is the value of k ?

(1) k*|k| = 4
(2) |k|*|k| = 4


Par of GMAT CLUB'S New Year's Quantitative Challenge Set

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Re: What is the value of k ? (1) k*|k| = 4 (2) |k|*|k| = 4 [#permalink] New post   09 Jan 2020, 07:58
Can k be sqrt(4)? I got this one right but then the thought just crossed my mind. absolute is the distance of K to 0. Does k have to be an integer?

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Re: What is the value of k ? (1) k*|k| = 4 (2) |k|*|k| = 4 [#permalink] New post   09 Jan 2020, 08:10
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lanml92 wrote:
Can k be sqrt(4)? I got this one right but then the thought just crossed my mind. absolute is the distance of K to 0. Does k have to be an integer?

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k does not have to be an integer but \(\sqrt{4}=2\), so...
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Re: What is the value of k ? (1) k*|k| = 4 (2) |k|*|k| = 4 [#permalink] New post   09 Jan 2020, 08:22
I realized I was being stupid right after I posted it but didn’t know how to delete the post. Thanks Bunuel anw.

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Re: What is the value of k ? (1) k*|k| = 4 (2) |k|*|k| = 4 [#permalink] New post   11 Oct 2021, 14:58
Asked: What is the value of k ?

(1) k*|k| = 4
If k = 2 ; k* |k| = 2 * 2 = 4
If k=-2; k* |k| = -2 * 2 = -4
k = 2
SUFFICIENT

(2) |k|*|k| = 4
If k = 2 ; |k|* |k| = 2 * 2 = 4
If k=-2; |k|* |k| = 2 * 2 = 4
NOT SUFFICIENT

IMO A
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Re: What is the value of k ? (1) k*|k| = 4 (2) |k|*|k| = 4 [#permalink]
11 Oct 2021, 14:58
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