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: What is the Value of xyz? [#permalink]
26 Dec 2013, 09:57

1

This post received KUDOS

Expert's post

suk1234 wrote:

What is the value ofxyz?

1) xyz - xy = 0 2) Either x=0, or y=0 or z=1

The see the OA, I think it's incorrect. What's your opinion?

Dear suk1234, I'm happy to respond.

I think the OA of (E) is correct. First of all, Statement #1 and Statement #2 are logical equivalent, and one implies the other. If x = 0 or y = 0, then the other could equal anything, z could equal anything, and the product would be zero. If z = 1, then x & y could equal anything, and the product could equal any value on the continuous infinity of the number line. Thus, there's no way to determine a definitive value of the product.

Does this make sense? Please let me know if you have any further questions. Mike _________________

Re: What is the Value of xyz? [#permalink]
26 Dec 2013, 10:11

mikemcgarry wrote:

suk1234 wrote:

What is the value ofxyz?

1) xyz - xy = 0 2) Either x=0, or y=0 or z=1

The see the OA, I think it's incorrect. What's your opinion?

Dear suk1234, I'm happy to respond.

I think the OA of (E) is correct. First of all, Statement #1 and Statement #2 are logical equivalent, and one implies the other. If x = 0 or y = 0, then the other could equal anything, z could equal anything, and the product would be zero. If z = 1, then x & y could equal anything, and the product could equal any value on the continuous infinity of the number line. Thus, there's no way to determine a definitive value of the product.

Does this make sense? Please let me know if you have any further questions. Mike

Thank you Mike for the Quick rescue!

Here is how I evaluated Statement 1:

Z=1 and Either X=0 or Y=0 or Both X and Y = 0

Then evaluate all the possible values! 1. (X=0) 0*Y*1=0 2. (Y=0) X*0*1=0 3. (X and Y = 0) 0*0*1=0

I think in case of statement 2 this reasoning doesn't apply because it presents three cases which may or may not be true ( x=0, or y=0 or z=1 either of these can happen or not). But in case of statement 1 we are definitely sure about the value of XY.

Re: What is the Value of xyz? [#permalink]
26 Dec 2013, 14:14

1

This post received KUDOS

Expert's post

suk1234 wrote:

Thank you Mike for the Quick rescue!

Here is how I evaluated Statement 1:

Z=1 and Either X=0 or Y=0 or Both X and Y = 0

Then evaluate all the possible values! 1. (X=0) 0*Y*1=0 2. (Y=0) X*0*1=0 3. (X and Y = 0) 0*0*1=0

I think in case of statement 2 this reasoning doesn't apply because it presents three cases which may or may not be true ( x=0, or y=0 or z=1 either of these can happen or not). But in case of statement 1 we are definitely sure about the value of XY.

Dear suk1234 I'm happy to respond.

Statement #1 says xyz - xy = 0 Add xy to both sides: xyz = xy (xy)*z = (xy)

Here, we are presented with a choice. Case One: If (xy) does not equal zero, then we can divide by (xy), and get z = 1. That's one case, in which (xy) can have any value on the number line other than zero, and z = 1. Here, the product xyz would be equal to xy, and could be anything other than zero. Case Two: If (xy) = 0, then z could be anything on the number line. This is the other case. If (xy) = 0, then either x = 0 or y = 0, which will make the product equal zero. (Here, z could be 1, or it could be anything else on the number line.)

You see, the crucial mathematical word is the word "or" ---- either z = 1 OR (xy) = 0. You are interpreting the two requirements as if they are simultaneous, not a mutually exclusive choice. The two cases are actually mutually exclusive.

Re: What is the Value of xyz? [#permalink]
27 Dec 2013, 00:48

mikemcgarry wrote:

suk1234 wrote:

Thank you Mike for the Quick rescue!

Here is how I evaluated Statement 1:

Z=1 and Either X=0 or Y=0 or Both X and Y = 0

Then evaluate all the possible values! 1. (X=0) 0*Y*1=0 2. (Y=0) X*0*1=0 3. (X and Y = 0) 0*0*1=0

I think in case of statement 2 this reasoning doesn't apply because it presents three cases which may or may not be true ( x=0, or y=0 or z=1 either of these can happen or not). But in case of statement 1 we are definitely sure about the value of XY.

Dear suk1234 I'm happy to respond.

Statement #1 says xyz - xy = 0 Add xy to both sides: xyz = xy (xy)*z = (xy)

Here, we are presented with a choice. Case One: If (xy) does not equal zero, then we can divide by (xy), and get z = 1. That's one case, in which (xy) can have any value on the number line other than zero, and z = 1. Here, the product xyz would be equal to xy, and could be anything other than zero. Case Two: If (xy) = 0, then z could be anything on the number line. This is the other case. If (xy) = 0, then either x = 0 or y = 0, which will make the product equal zero. (Here, z could be 1, or it could be anything else on the number line.)

You see, the crucial mathematical word is the word "or" ---- either z = 1 OR (xy) = 0. You are interpreting the two requirements as if they are simultaneous, not a mutually exclusive choice. The two cases are actually mutually exclusive.

Does all this make sense? Mike

Oh I see, where I was going wrong with it.Thank Mike that was an amazing explanation.

gmatclubot

Re: What is the Value of xyz?
[#permalink]
27 Dec 2013, 00:48

It’s been a long time, since I posted. A busy schedule at office and the GMAT preparation, fully tied up with all my free hours. Anyways, now I’m back...

Ah yes. Funemployment. The time between when you quit your job and when you start your MBA. The promised land that many MBA applicants seek. The break that every...

It is that time of year again – time for Clear Admit’s annual Best of Blogging voting. Dating way back to the 2004-2005 application season, the Best of Blogging...