GMAT Question of the Day - Daily to your Mailbox; hard ones only

It is currently 21 Feb 2019, 14:10

Close

GMAT Club Daily Prep

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.

Close

Request Expert Reply

Confirm Cancel
Events & Promotions in February
PrevNext
SuMoTuWeThFrSa
272829303112
3456789
10111213141516
17181920212223
242526272812
Open Detailed Calendar
  • Online GMAT boot camp for FREE

     February 21, 2019

     February 21, 2019

     10:00 PM PST

     11:00 PM PST

    Kick off your 2019 GMAT prep with a free 7-day boot camp that includes free online lessons, webinars, and a full GMAT course access. Limited for the first 99 registrants! Feb. 21st until the 27th.
  • Free GMAT RC Webinar

     February 23, 2019

     February 23, 2019

     07:00 AM PST

     09:00 AM PST

    Learn reading strategies that can help even non-voracious reader to master GMAT RC. Saturday, February 23rd at 7 AM PT

What is the value of y? (1) 2 x + 2 y = 14 (2) 2 y + 2 z = 14

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:

Hide Tags

 
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 53063
What is the value of y? (1) 2 x + 2 y = 14 (2) 2 y + 2 z = 14  [#permalink]

Show Tags

New post 21 Mar 2016, 06:17
1
1
00:00
A
B
C
D
E

Difficulty:

  5% (low)

Question Stats:

93% (00:49) correct 7% (01:02) wrong based on 178 sessions

HideShow timer Statistics

Intern
Intern
avatar
B
Joined: 13 Apr 2015
Posts: 32
GMAT ToolKit User
Re: What is the value of y? (1) 2 x + 2 y = 14 (2) 2 y + 2 z = 14  [#permalink]

Show Tags

New post 21 Mar 2016, 10:00
Is the answer E ? As we do not have any further information between x and z.We have two eq and 3 variables
CEO
CEO
User avatar
D
Joined: 11 Sep 2015
Posts: 3445
Location: Canada
What is the value of y? (1) 2 x + 2 y = 14 (2) 2 y + 2 z = 14  [#permalink]

Show Tags

New post Updated on: 07 Aug 2016, 12:33
Bunuel wrote:
What is the value of y?

(1) 2x + 2y = 14
(2) 2y + 2z = 14


Target question: What is the value of y?

Statement 1: 2x + 2y = 14
Simplify by dividing both sides by 2 to get: x + y = 7
This statement doesn't FEEL sufficient, so I'll TEST some values.
There are several values of x and y that satisfy statement 1. Here are two:
Case a: x = 0 and y = 7. Here, y = 7
Case b: x = 1 and y = 6. Here, y = 6
Since we cannot answer the target question with certainty, statement 1 is NOT SUFFICIENT

Aside: For more on this idea of plugging in values when a statement doesn't feel sufficient, you can read my article: http://www.gmatprepnow.com/articles/dat ... lug-values

Statement 2: 2y + 2z = 14
Simplify by dividing both sides by 2 to get: y + z = 7
There are several values of y and z that satisfy statement 1. Here are two:
Case a: y = 7 and z = 0. Here, y = 7
Case b: y = 6 and z = 1. Here, y = 6
Since we cannot answer the target question with certainty, statement 2 is NOT SUFFICIENT

Statements 1 and 2 combined
Statement 1 tells us that x + y = 7
Statement 2 tells us that z + y = 7
If we subtract the bottom equation from the top, we get x - z = 0
This means that x = z. That's ALL we can conclude when we COMBINE the statements.
As such, there's no way to determine the value of y.
Since we cannot answer the target question with certainty, the combined statements are NOT SUFFICIENT
Answer =

Aside: If we want to be 100% sure of our answer consider these values of x, y and z that satisfy BOTH equations:
Case a: x = 0, y = 7 and z = 0. Here, y = 7
Case b: x = 1, y = 6 and z = 1. Here, y = 6

Cheers,
Brent
_________________

Test confidently with gmatprepnow.com
Image


Originally posted by GMATPrepNow on 21 Mar 2016, 14:58.
Last edited by GMATPrepNow on 07 Aug 2016, 12:33, edited 1 time in total.
Math Revolution GMAT Instructor
User avatar
V
Joined: 16 Aug 2015
Posts: 6978
GMAT 1: 760 Q51 V42
GPA: 3.82
Premium Member
Re: What is the value of y? (1) 2 x + 2 y = 14 (2) 2 y + 2 z = 14  [#permalink]

Show Tags

New post 21 Mar 2016, 17:36
Forget conventional ways of solving math questions. In DS, Variable approach is the easiest and quickest way to find the answer without actually solving the problem. Remember equal number of variables and independent equations ensures a solution.

What is the value of y?

(1) 2 x + 2 y = 14

(2) 2 y + 2 z = 14


In the original condition, there are 3 variables(x,y,z), which should match with the number of equations. So you need 3 equations. For 1) 1 equation, for 2) 1 equation, which is likely to make E the answer. When 1) & 2), the value of y is not unique, which is not sufficient.
Therefore, the answer is E.


 For cases where we need 3 more equations, such as original conditions with “3 variables”, or “4 variables and 1 equation”, or “5 variables and 2 equations”, we have 1 equation each in both 1) and 2). Therefore, there is 80% chance that E is the answer (especially about 90% of 2 by 2 questions where there are more than 3 variables), while C has 15% chance. These two are the majority. In case of common mistake type 3,4, the answer may be from A, B or D but there is only 5% chance. Since E is most likely to be the answer using 1) and 2) separately according to DS definition (It saves us time). Obviously there may be cases where the answer is A, B, C or D.
_________________

MathRevolution: Finish GMAT Quant Section with 10 minutes to spare
The one-and-only World’s First Variable Approach for DS and IVY Approach for PS with ease, speed and accuracy.
"Only $149 for 3 month Online Course"
"Free Resources-30 day online access & Diagnostic Test"
"Unlimited Access to over 120 free video lessons - try it yourself"

Director
Director
avatar
S
Joined: 12 Nov 2016
Posts: 725
Location: United States
Schools: Yale '18
GMAT 1: 650 Q43 V37
GRE 1: Q157 V158
GPA: 2.66
Re: What is the value of y? (1) 2 x + 2 y = 14 (2) 2 y + 2 z = 14  [#permalink]

Show Tags

New post 10 Sep 2017, 11:58
1
Bunuel wrote:
What is the value of y?

(1) 2 x + 2 y = 14

(2) 2 y + 2 z = 14


This question plays a very subtle trick

x + y = 7

z + y= 7

therefore

x=z

HOWEVER

Just x=z that doesn't necessarily mean that the value of Y can be identified as Y can be several things.

E
Non-Human User
User avatar
Joined: 09 Sep 2013
Posts: 9879
Premium Member
Re: What is the value of y? (1) 2 x + 2 y = 14 (2) 2 y + 2 z = 14  [#permalink]

Show Tags

New post 19 Jan 2019, 07:34
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.
_________________

GMAT Books | GMAT Club Tests | Best Prices on GMAT Courses | GMAT Mobile App | Math Resources | Verbal Resources

GMAT Club Bot
Re: What is the value of y? (1) 2 x + 2 y = 14 (2) 2 y + 2 z = 14   [#permalink] 19 Jan 2019, 07:34
Display posts from previous: Sort by

What is the value of y? (1) 2 x + 2 y = 14 (2) 2 y + 2 z = 14

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  


Copyright

GMAT Club MBA Forum Home| About| Terms and Conditions and Privacy Policy| GMAT Club Rules| Contact| Sitemap

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne

Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.