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.

It appears that you are browsing the GMAT Club forum unregistered!

Signing up is free, quick, and confidential.
Join other 500,000 members and get the full benefits of GMAT Club

Registration gives you:

Tests

Take 11 tests and quizzes from GMAT Club and leading GMAT prep companies such as Manhattan GMAT,
Knewton, and others. All are free for GMAT Club members.

Applicant Stats

View detailed applicant stats such as GPA, GMAT score, work experience, location, application
status, and more

Books/Downloads

Download thousands of study notes,
question collections, GMAT Club’s
Grammar and Math books.
All are free!

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:

Fence X is twice as long as fence Y, and fence Y is 2 feet shorter tha [#permalink]

Show Tags

28 Mar 2014, 17:58

1

This post was BOOKMARKED

00:00

A

B

C

D

E

Difficulty:

55% (hard)

Question Stats:

54% (02:38) correct
46% (01:38) wrong based on 124 sessions

HideShow timer Statistics

Fence X is twice as long as fence Y, and fence Y is 2 feet shorter than fence Z. If 3 feet were added to each fence, which of the following must be true?

I) X is twice as long as Y. II) Y is 2 feet shorter than Z. III) X is longer than Z.

A) I only B) II only C) III only D) I and II E) II and III

Encourage cooperation! If this post was very useful, kudos are welcome "It is our attitude at the beginning of a difficult task which, more than anything else, will affect It's successful outcome" William James

Re: Fence X is twice as long as fence Y, and fence Y is 2 feet shorter tha [#permalink]

Show Tags

28 Mar 2014, 23:43

1

This post received KUDOS

Expert's post

Maxirosario2012 wrote:

Fence X is twice as long as fence Y, and fence Y is 2 feet shorter than fence Z. If 3 feet were added to each fence, which of the following must be true?

I) X is twice as long as Y. II) Y is 2 feet shorter than Z. III) X is longer than Z.

A) I only B) II only C) III only D) I and II E) II and III

Length of Z = z Length of Y = z-2 Length of X = 2z-4

Minimum possible length of fence Z is 2 feet, because if we take the value for length of z below 2, lengths of Z and Y would be negative which is not possible.

If Z = 2 then Y = 0 and X = 0

When we add 3 feet in each fence, we will get Z= 5 Y=3 X=3

Only Statement II holds true with above values. _________________

Re: Fence X is twice as long as fence Y, and fence Y is 2 feet shorter tha [#permalink]

Show Tags

29 Mar 2014, 12:04

Thank you Narenn. I posted this problem because Kaplan suggest to use the "picking numbers" strategy. But I think that backsolving is not the best approach. Why?:

If X= 6 Y= 3 Z= 5

Then, after adding 3 feet to each:

X= 9 Y=6 Z=8

And the answer would be E, which is wrong. _________________

Encourage cooperation! If this post was very useful, kudos are welcome "It is our attitude at the beginning of a difficult task which, more than anything else, will affect It's successful outcome" William James

Re: Fence X is twice as long as fence Y, and fence Y is 2 feet shorter tha [#permalink]

Show Tags

31 Mar 2014, 12:50

X = 2Y and Z = Y+2 are given to us to be true according to the question.

1) (X+3) = 2(Y+3) => X + 3 = 2Y + 6 => X = 2Y +3, which cannot be true as X=2Y. NEVER TRUE--> REJECT. 2) (Y+3) + 2 = Z+3 => Y+2 = Z, which is true. ALWAYS TRUE --> ACCEPT. 3) X+3 > Z+3 => X>Z => 2Y > (Y+2) => Y>2. So this is true only if Y>2, else it is false. We can check this out quickly. If X=2, Y=1, Z=4, then X<Z, but if X=6,Y=3,Z=5, then X>Z. CONDITIONALLY TRUE --> REJECT.

Therefore the answer must be (B). _________________

Re: Fence X is twice as long as fence Y, and fence Y is 2 feet shorter tha [#permalink]

Show Tags

31 Mar 2014, 22:00

2

This post received KUDOS

Expert's post

Maxirosario2012 wrote:

Thank you Narenn. I posted this problem because Kaplan suggest to use the "picking numbers" strategy. But I think that backsolving is not the best approach. Why?:

If X= 6 Y= 3 Z= 5

Then, after adding 3 feet to each:

X= 9 Y=6 Z=8

And the answer would be E, which is wrong.

You are correct. Number plugging in almost never a good approach when you have to prove that something MUST BE TRUE. To prove that something will be true in every case, how many cases are sufficient? Can I check 2 cases and say that it will be true in every case? Should I check 6, or 20? Even if something is true in 20 cases, it may not hold for the 21st case! We must use logic to prove that something must be true in every case. But we can use number plugging to disprove something. i.e. we try to find the case in which it doesn't hold and then we can say that something needn't be true in every case.

Just taking the example of X = 6 (you took one case), you cannot say that II and III must be true. All you can say is that I certainly is not true in every case.

Using logic: "X is twice as long as fence Y" "fence Y is 2 feet shorter than fence Z" "3 feet were added to each fence"

I) X is twice as long as Y. X is originally twice as long as Y. When we add 3 to both, X will no longer be twice. Not true.

II) Y is 2 feet shorter than Z. Originally, Y was 2 feet shorter than Z. If you add equal length to both (i.e. 3 feet) , Y will still remain 2 feet shorter than Z. Always true.

III) X is longer than Z. X is twice of Y (hence X greater than Y) and Z is 2 more than Y (Z is greater than Y too). Both X and Z are greater than Y so we don't know what is the relation between X and Z. Say if Y = 1, Z = 3 and X = 2. So X needn't be longer than Z. _________________

Re: Fence X is twice as long as fence Y, and fence Y is 2 feet shorter tha [#permalink]

Show Tags

31 Mar 2014, 22:27

Narenn wrote:

Maxirosario2012 wrote:

Fence X is twice as long as fence Y, and fence Y is 2 feet shorter than fence Z. If 3 feet were added to each fence, which of the following must be true?

I) X is twice as long as Y. II) Y is 2 feet shorter than Z. III) X is longer than Z.

A) I only B) II only C) III only D) I and II E) II and III

Length of Z = z Length of Y = z-2 Length of X = 2z-4

Minimum possible length of fence Z is 2 feet, because if we take the value for length of z below 2, lengths of Z and Y would be negative which is not possible.

If Z = 2 then Y = 0 and X = 0

When we add 3 feet in each fence, we will get Z= 5 Y=3 X=3

Only Statement II holds true with above values.

if Z=2, Y=0 and X=0 then X/Y not equal 2, so minimal cases is Z=3, Y=1 and X=2. The critical is that if X<Z or X=Z these facts make III wrong

Re: Fence X is twice as long as fence Y, and fence Y is 2 feet shorter tha [#permalink]

Show Tags

29 Jan 2016, 23:47

Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email. _________________

Excellent posts dLo saw your blog too..!! Man .. you have got some writing skills. And Just to make an argument = You had such an amazing resume ; i am glad...

So Much $$$ Business school costs a lot. This is obvious, whether you are a full-ride scholarship student or are paying fully out-of-pocket. Aside from the (constantly rising)...

London is the best kept secret of the corporate world. It is English speaking and time delayed by only 5 hours. That means when London goes home at 5...