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 Your Progress

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

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:

Re: Inequality Problem [#permalink]
01 Aug 2010, 13:15

1

This post received KUDOS

is |x|=y-z?

given: (1) x+y=z (2) x<0

solving (1) first:

y=z-x |x|=(z-x)-z |x|=-x

take x=1, z=2, y=1 1=1-2 (no) take x=-1, z=2, y=3 |x|=y-z? |-1|=3-2=1 YES

so what solving for |x|=-x meant was that x MUST be negative for the equation to be true, if it is positive then it is not true (since in that case, |x| would not equal -x).

(1) Can be rewritten as X = -Y + Z, so |X| = |-Y + Z|, which would be equal to Y - Z, if and only if -Y+Z\leq0. Obviously, we don't know that, so (1) insufficient. (2) Cannot be sufficient, it doesn't say anything about Y and Z. (1) and (2) together: X = -Y + Z < 0, therefore |X| = Y - Z, sufficient.

Answer: C

_________________

PhD in Applied Mathematics Love GMAT Quant questions and running.

Re: Abs equation from GMATPrep [#permalink]
25 Nov 2012, 17:17

1

This post received KUDOS

The question poses as x being the centerpiece variable but Bunuel turns it on its face and makes y-z the main subject. Which makes all the difference with data pt 1 when u look at it as y-z=-x. You immediately see that the right side has to be -ve for the LEft side to be +ve. Brilliant approach.

Bunuel wrote:

Is |x|=y-z?

Note that y-z must be \geq{0}, because absolute value (in our case |x|) can not be negative.

Generally question asks whether y-z\geq{0}and whether the difference between them equals to |x|.

(1) -x=y-z if x>0 --> y-z is negative --> no good for us; if x\leq{0} --> y-z is positive --> good. Two possible answers not sufficient;

(2) x<0 Not sufficient (we need to know value of y-z is equal or not to |x|)

Re: Abs equation from GMATPrep [#permalink]
05 Oct 2012, 04:44

Bunuel wrote:

Is |x|=y-z?

Note that y-z must be \geq{0}, because absolute value (in our case |x|) can not be negative.

Generally question asks whether y-z\geq{0}and whether the difference between them equals to |x|.

(1) -x=y-z if x>0 --> y-z is negative --> no good for us; if x\leq{0} --> y-z is positive --> good. Two possible answers not sufficient;

(2) x<0 Not sufficient (we need to know value of y-z is equal or not to |x|)

(1)+(2) Sufficient.

Answer: C.

Hi bunuel, I am not able to understand the solution for this problem. Can you kindly explain the highlighted areas. Note that y-z must be \geq{0}, because absolute value (in our case |x|) can not be negative.

Generally question asks whether y-z\geq{0} and whether the difference between them equals to |x|.

(1) -x=y-z if x>0 --> y-z is negative --> no good for us; if x\leq{0} --> y-z is positive --> good.

Waiting for reply.

_________________

If you like my Question/Explanation or the contribution, Kindly appreciate by pressing KUDOS. Kudos always maximizes GMATCLUB worth-Game Theory

If you have any question regarding my post, kindly pm me or else I won't be able to reply

Re: Abs equation from GMATPrep [#permalink]
05 Oct 2012, 05:12

Expert's post

fameatop wrote:

Bunuel wrote:

Is |x|=y-z?

Note that y-z must be \geq{0}, because absolute value (in our case |x|) can not be negative.

Generally question asks whether y-z\geq{0}and whether the difference between them equals to |x|.

(1) -x=y-z if x>0 --> y-z is negative --> no good for us; if x\leq{0} --> y-z is positive --> good. Two possible answers not sufficient;

(2) x<0 Not sufficient (we need to know value of y-z is equal or not to |x|)

(1)+(2) Sufficient.

Answer: C.

Hi bunuel, I am not able to understand the solution for this problem. Can you kindly explain the highlighted areas. Note that y-z must be \geq{0}, because absolute value (in our case |x|) can not be negative.

Generally question asks whether y-z\geq{0} and whether the difference between them equals to |x|.

(1) -x=y-z if x>0 --> y-z is negative --> no good for us; if x\leq{0} --> y-z is positive --> good.

Waiting for reply.

Look at |x|=y-z: the left hand side is absolute value (|x|), which cannot be negative, hence the right hand side (y-z) also cannot be negative. Therefore must be true that y-z\geq{0}.

Next, for (1) given that -x=y-z. Now, if x>0, or if x is positive, then we'll have that -positive =y-z --> negative=y-z. But as we concluded above y-z cannot be negative, hence this scenario is not good.