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Is the point (x,y) in the fourth quadrant? [#permalink]
06 Oct 2009, 18:26

3

This post received KUDOS

00:00

A

B

C

D

E

Difficulty:

35% (medium)

Question Stats:

50% (01:09) correct
50% (00:23) wrong based on 24 sessions

I recently took a practice test with my iPhone software (GMAT Math ver 1.1) and got a question I don't altogether agree with. Can someone help me out here?

DS Question: Is the point (x,y) in the fourth quadrant)? 1) xy >0 2) y > 0

The software says 1 alone is sufficient, but I think you need both. My reasoning is that x could be -2 and y=-2, in that case, xy = 4 > 0. That would put the point in the 3rd quadrant while 2,2 would also fulfill that and put it in the 1st quad. Therefore 1 alone shouldn't be enough to be conclusive.

Re: an error in my iphone software? Or just an oversight... [#permalink]
06 Oct 2009, 18:41

1

This post received KUDOS

Expert's post

Jones105 wrote:

I recently took a practice test with my iPhone software (GMAT Math ver 1.1) and got a question I don't altogether agree with. Can someone help me out here?

DS Question: Is the point (x,y) in the fourth quadrant)? 1) xy >0 2) y > 0

The software says 1 alone is sufficient, but I think you need both. My reasoning is that x could be -2 and y=-2, in that case, xy = 4 > 0. That would put the point in the 3rd quadrant while 2,2 would also fulfill that and put it in the 1st quad. Therefore 1 alone shouldn't be enough to be conclusive.

thanks for any insights...

This is yes/no DS problem:

(1) xy>0 --> x an y have same signs --> the point is either in I or III in quadrant, so you can answer the question "Is the point (x,y) in the fourth quadrant" - NO. Sufficient

(2) y>0 --> the point is either in I or in II quadrant. Again Sufficient to answer the question: No it's not in 4th quadrant. Sufficient

D.

In the 4th quadrant y is negative x is positive and xy<o

Does your software say the answer is A? If so it's not right. Answer is D each alone is sufficient. _________________

Re: an error in my iphone software? Or just an oversight... [#permalink]
06 Oct 2009, 19:37

Ahh, I missed the trees for the forest.

You're right, being in 1 or 3 would in fact negate the possibility of being in 4. I was thinking in terms of, is it sufficient to determine what quadrant it's in.

Re: an error in my iphone software? Or just an oversight... [#permalink]
07 Oct 2009, 00:48

Yes, there is an error. I guess we'll have to change S2 to 2) y \lt 0 We won't have the problem then. What do you guys think? Sorry about the error. _________________

Re: an error in my iphone software? Or just an oversight... [#permalink]
07 Oct 2009, 06:13

Thanks! If I have any other questions as I use the software, should I PM you, or start a new thread somewhere? I'm sure most of the time it will just be my oversights.

Re: an error in my iphone software? Or just an oversight... [#permalink]
07 Oct 2009, 06:24

Feel free to PM me or BB regarding this software. Thank you.

Jones105 wrote:

Thanks! If I have any other questions as I use the software, should I PM you, or start a new thread somewhere? I'm sure most of the time it will just be my oversights.

Re: an error in my iphone software? Or just an oversight... [#permalink]
07 Oct 2009, 19:15

Expert's post

Jones105 wrote:

I recently took a practice test with my iPhone software (GMAT Math ver 1.1) and got a question I don't altogether agree with. Can someone help me out here?

DS Question: Is the point (x,y) in the fourth quadrant)? 1) xy >0 2) y > 0

The software says 1 alone is sufficient, but I think you need both. My reasoning is that x could be -2 and y=-2, in that case, xy = 4 > 0. That would put the point in the 3rd quadrant while 2,2 would also fulfill that and put it in the 1st quad. Therefore 1 alone shouldn't be enough to be conclusive.

thanks for any insights...

Jones - can you tell me the question number in the GMAT Club App? I am not able to locate this question - are you sure it is from our Application? _________________

Re: an error in my iphone software? Or just an oversight... [#permalink]
08 Oct 2009, 00:01

Hah, I guess before we all get carried away, we should probably make sure we're talking about the same software, eh?

As I said above, I'm using GMAT MATH version 1.1 by Indriam Inc.

I just searched the app Store (I'm in Japan using a US account) for "gmat math" and it was the second result, labeled as GMAT Math Review for $2.99 by Indriam Inc.

I took the mini Test (19 questions) and it was question number 17 in that test, but I'm guessing it's different each time?

Re: an error in my iphone software? Or just an oversight... [#permalink]
08 Oct 2009, 00:02

Expert's post

Jones105 wrote:

Hah, I guess before we all get carried away, we should probably make sure we're talking about the same software, eh?

As I said above, I'm using GMAT MATH version 1.1 by Indriam Inc.

I just searched the app Store (I'm in Japan using a US account) for "gmat math" and it was the second result, labeled as GMAT Math Review for $2.99 by Indriam Inc.

I took the mini Test (19 questions) and it was question number 17 in that test, but I'm guessing it's different each time?

Re: an error in my iphone software? Or just an oversight... [#permalink]
08 Oct 2009, 00:06

Jones105 wrote:

I recently took a practice test with my iPhone software (GMAT Math ver 1.1) and got a question I don't altogether agree with. Can someone help me out here?

...

thanks for any insights...

Hmm, your above posts got me intrigued and I've done some more research. I did find the GMAT Club software on the app store (and just purchased it) but my post was never intended to reference that app. Perhaps "GMAT Math" software on the iphone is too generic a term.

Re: an error in my iphone software? Or just an oversight... [#permalink]
08 Oct 2009, 00:16

Expert's post

Jones105 wrote:

Jones105 wrote:

I recently took a practice test with my iPhone software (GMAT Math ver 1.1) and got a question I don't altogether agree with. Can someone help me out here?

...

thanks for any insights...

Hmm, your above posts got me intrigued and I've done some more research. I did find the GMAT Club software on the app store (and just purchased it) but my post was never intended to reference that app. Perhaps "GMAT Math" software on the iphone is too generic a term.

Sorry for any trouble!

No worries at all - any feedback about the app is welcome! _________________