og 105 ds

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resilient: Legendary Member; Posts: 789; Joined: Sun May 06, 2007 1:25 amFollowed by: 6 members; Location: Southern California, USA; Thanked: 15 times

by resilient » Fri Feb 08, 2008 6:14 pm

Is absolute value x = y-z?

1. x=y=z
2. x<0

i dont see how c is the correct answer when I get iconsistent outcomes 1. yes and 1 no when plugging in numbers.. Help please

qa is c

Appetite for 700 and I scraped my plate!

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Source: Beat The GMAT — Data Sufficiency | Fri Feb 08, 2008 6:14 pm

si1ent: Newbie | Next Rank: 10 Posts; Posts: 3; Joined: Thu Feb 28, 2008 4:50 pm

Re: og 105 ds

by si1ent » Sat Apr 05, 2008 12:16 am

Enginpasa1 wrote:Is absolute value x = y-z?

1. x+y=z
2. x<0

i dont see how c is the correct answer when I get iconsistent outcomes 1. yes and 1 no when plugging in numbers.. Help please

qa is c

for some absolute reason, i can't comprehend this. i feel my IQ dropping.

in my mind, to rephrase the question:

-is the distance of |X| from zero (y-z)?

1) x=z-y
-or-
x= -(-z+y)
-or-
-x=(y-z)

so that tells me positive X's distance from zero is (z-y)
and negative X's distance from zero is (y-z)

now shouldn't the absolute distance of X from zero be the same regardless of whether it's negative or positive?

What am i missing?

thanks!

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si1ent: Newbie | Next Rank: 10 Posts; Posts: 3; Joined: Thu Feb 28, 2008 4:50 pm

Re: og 105 ds

by si1ent » Sat Apr 05, 2008 1:02 am

si1ent wrote:
Enginpasa1 wrote:Is absolute value x = y-z?

1. x+y=z
2. x<0

i dont see how c is the correct answer when I get iconsistent outcomes 1. yes and 1 no when plugging in numbers.. Help please

qa is c
for some absolute reason, i can't comprehend this. i feel my IQ dropping.

in my mind, to rephrase the question:

-is the distance of |X| from zero (y-z)?

1) x=z-y
-or-
x= -(-z+y)
-or-
-x=(y-z)

so that tells me positive X's distance from zero is (z-y)
and negative X's distance from zero is (y-z)

now shouldn't the absolute distance of X from zero be the same regardless of whether it's negative or positive?

What am i missing?

thanks!

quoting myself... |x| = y-z ?

e.g. distance of x is 7 from zero.

y=9
z=2

x is positive, then, 9-2 or x=y-z

x is negative, then -(9-2) or x= -(y-z)

1) x=z-y
x=2-9
x= -7

does this tell me that x is -7, therefore having a distance from zero of 7. since it's negative, then the equation is
|x| = |-(y-z)|.

ok i'm getting sleepy uggh..

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Stuart@KaplanGMAT: GMAT Instructor; Posts: 3225; Joined: Tue Jan 08, 2008 2:40 pmFollowed by: 614 members; Location: Toronto; Thanked: 1710 times; GMAT Score:800

Re: og 105 ds

by Stuart@KaplanGMAT » Sat Apr 05, 2008 8:16 am

Enginpasa1 wrote:Is absolute value x = y-z?

1. x=y=z
2. x<0

Is |x| = y - z?

So, we need to know about x and about y - z.

(1) x = y = z

let's substitute into the original question:

Is |x| = x - x

or

Is |x| = 0?

Well, if x = 0, yes it is. If x = anything else, no it isn't.

We can get a yes and a no: insufficient.

(2) x < 0

So what? Don't know anything about y and z: insufficient.

Combined:

Is |x| = 0?

Well, based on (2) x can no longer equal 0. Every non-0 value for x will give us a "no" answer to the question. So, when we combine we know that |x| is definitely NOT equal to y - z: choose (c).

Stuart Kovinsky | Kaplan GMAT Faculty | Toronto

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simplyjat: Master | Next Rank: 500 Posts; Posts: 423; Joined: Thu Dec 27, 2007 1:29 amFollowed by: 2 members; Location: Hyderabad, India; Thanked: 36 times; GMAT Score:770

Re: og 105 ds

by simplyjat » Sat Apr 05, 2008 9:20 am

Enginpasa1 wrote:Is absolute value x = y-z?

1. x=y=z
2. x<0

i dont see how c is the correct answer when I get iconsistent outcomes 1. yes and 1 no when plugging in numbers.. Help please
qa is c

Please pay more attention while typing the question. The original question reads

1. x+y=z

simplyjat

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resilient: Legendary Member; Posts: 789; Joined: Sun May 06, 2007 1:25 amFollowed by: 6 members; Location: Southern California, USA; Thanked: 15 times

hmm

by resilient » Sat Apr 05, 2008 11:22 am

my apologies! x+y=z corrected

Appetite for 700 and I scraped my plate!

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