Find the integer K: (1) K*|K|=4 (2) |K|*|K|=4 : Quant Question Archive [LOCKED]
Check GMAT Club Decision Tracker for the Latest School Decision Releases http://gmatclub.com/AppTrack

 It is currently 18 Jan 2017, 14:16

### GMAT Club Daily Prep

#### Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# Find the integer K: (1) K*|K|=4 (2) |K|*|K|=4

Author Message
SVP
Joined: 03 Feb 2003
Posts: 1603
Followers: 8

Kudos [?]: 245 [0], given: 0

Find the integer K: (1) K*|K|=4 (2) |K|*|K|=4 [#permalink]

### Show Tags

06 Jun 2003, 03:52
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

Find the integer K:

(1) K*|K|=4
(2) |K|*|K|=4
Manager
Joined: 03 Jun 2003
Posts: 84
Location: Uruguay
Followers: 1

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

### Show Tags

06 Jun 2003, 06:28
I also go with A

In A only chance is 2
In B either 2 or -2 work
Senior Manager
Joined: 22 Nov 2005
Posts: 476
Followers: 2

Kudos [?]: 20 [0], given: 0

### Show Tags

15 Mar 2006, 14:02
stolyar wrote:
A is correct

Can someone explain Why A

My logic is

K*|K| = 4

so |K| = +K if K > 0
= -K if K < 0

case 1 K > 0:

K * |K| = K * K = 4 ---> K^2 = 4 ---> K = +/- 2

Since K has two values so its not possible.

For case 2 K < 0

|K| = -k

==> K* (-k) = -K^2 = 4 -->>> which doesn't make any sense.

Can someone point out flaw in my derivation
Manager
Joined: 04 Jan 2006
Posts: 58
Followers: 1

Kudos [?]: 2 [0], given: 0

### Show Tags

15 Mar 2006, 14:45
stmt 1:
K*|k| =4
K has to be +2.

if k = -2, then k*|k| = -2*|-2| = -2*2 = -4
So stmt 1 is suff to know K = 2

stmt2:
|k|*|k| = 4
Here K can be +2 or -2. Both will result in 4.
So insuff.
GMAT Club Legend
Joined: 07 Jul 2004
Posts: 5062
Location: Singapore
Followers: 30

Kudos [?]: 357 [0], given: 0

### Show Tags

15 Mar 2006, 17:58
gmat_crack wrote:
stolyar wrote:
A is correct

Can someone explain Why A

My logic is

K*|K| = 4

so |K| = +K if K > 0
= -K if K < 0

case 1 K > 0:

K * |K| = K * K = 4 ---> K^2 = 4 ---> K = +/- 2

Since K has two values so its not possible.

For case 2 K < 0

|K| = -k

==> K* (-k) = -K^2 = 4 -->>> which doesn't make any sense.

Can someone point out flaw in my derivation

You're right that -K^2 = 4, but we know if we solve it, the result would be an imaginary number. Since the GMAT does not take imaginary numbers as a legitimate answer, st1 is deemed to be sufficient.
Manager
Joined: 30 Jan 2006
Posts: 145
Followers: 1

Kudos [?]: 25 [0], given: 0

### Show Tags

15 Mar 2006, 18:36
gmat_crack wrote:
stolyar wrote:

My logic is

K*|K| = 4

so |K| = +K if K > 0
= -K if K < 0

Can someone point out flaw in my derivation

Are you stating the following in your logic?:

so |K| = -K if K < 0

If yes, then that's where the flaw is... the absolut value of any given number can never be negative, only positive! Therefore, your statement "|K| = -K if K < 0" is incorrect.

Think of the absolute value of a given number as the "steps" it is away from zero. For example, -2 is two steps away from zero. Thus |-2| = 2.

The rest of the explanation is perfectly given by Nayan.
VP
Joined: 29 Dec 2005
Posts: 1348
Followers: 10

Kudos [?]: 60 [0], given: 0

### Show Tags

15 Mar 2006, 20:21
stolyar wrote:
Find the integer K:

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

from i, if k = -2, K*|K|= -4 which is not true.
if k = 2, K*|K|= 4 which is true. so the only possible value of k =2.

from ii, if k = 2, K*|K|= 4 which is true.
if k = -2 2, K*|K|= 4 which is also true. so here k can be + or - 2.

so only A is sufficient.

gmat_crack wrote:
stolyar wrote:
A is correct

Can someone explain Why A
My logic is
K*|K| = 4
so |K| = +K if K > 0
= -K if K < 0
case 1 K > 0:
K * |K| = K * K = 4 ---> K^2 = 4 ---> K = +/- 2
Since K has two values so its not possible.
For case 2 K < 0
|K| = -k
==> K* (-k) = -K^2 = 4 -->>> which doesn't make any sense.
Can someone point out flaw in my derivation
15 Mar 2006, 20:21
Display posts from previous: Sort by