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

It is currently 10 Dec 2018, 20:40

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 December
PrevNext
SuMoTuWeThFrSa
2526272829301
2345678
9101112131415
16171819202122
23242526272829
303112345
Open Detailed Calendar
  • Free lesson on number properties

     December 10, 2018

     December 10, 2018

     10:00 PM PST

     11:00 PM PST

    Practice the one most important Quant section - Integer properties, and rapidly improve your skills.
  • Free GMAT Prep Hour

     December 11, 2018

     December 11, 2018

     09:00 PM EST

     10:00 PM EST

    Strategies and techniques for approaching featured GMAT topics. December 11 at 9 PM EST.

If 2/z = 2/(z + 1) + 2/(z + 9) which of these integers could be the

  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: 51072
If 2/z = 2/(z + 1) + 2/(z + 9) which of these integers could be the  [#permalink]

Show Tags

New post 08 May 2015, 05:21
3
1
00:00
A
B
C
D
E

Difficulty:

  15% (low)

Question Stats:

85% (01:50) correct 15% (02:19) wrong based on 164 sessions

HideShow timer Statistics

Most Helpful Community Reply
Intern
Intern
User avatar
Joined: 05 Mar 2016
Posts: 8
Concentration: Finance, Strategy
Schools: Imperial '18
Re: If 2/z = 2/(z + 1) + 2/(z + 9) which of these integers could be the  [#permalink]

Show Tags

New post 08 Mar 2016, 13:03
5
z=3 2/3=2/4+2/2/12
2/3=1/2+1/6
2/3=2/3
LHS=RHS
oa= D
_________________

Please press 1 kudos if you like my post .Thanks

General Discussion
Manager
Manager
avatar
B
Joined: 12 Nov 2014
Posts: 63
CAT Tests
If 2/z = 2/(z + 1) + 2/(z + 9) which of these integers could be the  [#permalink]

Show Tags

New post Updated on: 10 May 2015, 20:38
1
Answer is z= 3.
One could easily pick numbers and check this within a minute.

But if we can rewrite the equation as (1/z) - (1/z+1) = 1/z+9. One can see that the left hand side is 1/z(z+1)
(For example 1/4- 1/5 = 1/20; 1/3-1/4 = 1/12; 1/9 - 1/10 = 1/90)
So you get z(z+1) = z+9. Now one can easily see that z=3 (One can also see that LHS is always even so RHS has to be even.So z has to be odd)

Answer : D
_________________

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Kindly press Kudos if the explanation is clear.
Thank you
Ambarish


Originally posted by askhere on 09 May 2015, 01:32.
Last edited by askhere on 10 May 2015, 20:38, edited 1 time in total.
Director
Director
avatar
P
Joined: 21 May 2013
Posts: 653
Re: If 2/z = 2/(z + 1) + 2/(z + 9) which of these integers could be the  [#permalink]

Show Tags

New post 09 May 2015, 11:44
1
Bunuel wrote:
If 2/z = 2/(z + 1) + 2/(z + 9) which of these integers could be the value of z?

(A) 0
(B) 1
(C) 2
(D) 3
(E) 4

Kudos for a correct solution.

Using different values given in the answer,
Put z=3
2/3=2/4+2/2/12
2/3=1/2+1/6
2/3=2/3
LHS=RHS
Answer D
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 51072
Re: If 2/z = 2/(z + 1) + 2/(z + 9) which of these integers could be the  [#permalink]

Show Tags

New post 11 May 2015, 05:51
1
Bunuel wrote:
If 2/z = 2/(z + 1) + 2/(z + 9) which of these integers could be the value of z?

(A) 0
(B) 1
(C) 2
(D) 3
(E) 4

Kudos for a correct solution.


MANHATTAN GMAT OFFICIAL SOLUTION:

Solving for z algebraically in this problem would not be easy. Instead, we can follow the hint in the question (“which of these integers…”) and test each answer choice:

A. 2/0 = 2/1 +2/9 INCORRECT (Division by zero)
A. 2/1 = 2/2 +2/10 INCORRECT
A. 2/2 = 2/3 +2/11 INCORRECT
A. 2/3 = 2/4 +2/12 CORRECT
A. 2/4 = 2/5 +2/13 INCORRECT

The correct answer is D, because it contains the only value that makes the equation work. Notice how quickly this strategy worked in this case
_________________

New to the Math Forum?
Please read this: Ultimate GMAT Quantitative Megathread | All You Need for Quant | PLEASE READ AND FOLLOW: 12 Rules for Posting!!!

Resources:
GMAT Math Book | Triangles | Polygons | Coordinate Geometry | Factorials | Circles | Number Theory | Remainders; 8. Overlapping Sets | PDF of Math Book; 10. Remainders | GMAT Prep Software Analysis | SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) | Tricky questions from previous years.

Collection of Questions:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.


What are GMAT Club Tests?
Extra-hard Quant Tests with Brilliant Analytics

Current Student
User avatar
D
Joined: 12 Aug 2015
Posts: 2630
Schools: Boston U '20 (M)
GRE 1: Q169 V154
GMAT ToolKit User Premium Member
Re: If 2/z = 2/(z + 1) + 2/(z + 9) which of these integers could be the  [#permalink]

Show Tags

New post 08 Mar 2016, 09:40
1
askhere wrote:
Answer is z= 3.
One could easily pick numbers and check this within a minute.

But if we can rewrite the equation as (1/z) - (1/z+1) = 1/z+9. One can see that the left hand side is 1/z(z+1)
(For example 1/4- 1/5 = 1/20; 1/3-1/4 = 1/12; 1/9 - 1/10 = 1/90)
So you get z(z+1) = z+9. Now one can easily see that z=3 (One can also see that LHS is always even so RHS has to be even.So z has to be odd)

Answer : D


Although your approach is perfectly fine but i think using the options and plugging in the values would be more easy in here.
_________________


MBA Financing:- INDIAN PUBLIC BANKS vs PRODIGY FINANCE!

Getting into HOLLYWOOD with an MBA!

The MOST AFFORDABLE MBA programs!

STONECOLD's BRUTAL Mock Tests for GMAT-Quant(700+)

AVERAGE GRE Scores At The Top Business Schools!

Non-Human User
User avatar
Joined: 09 Sep 2013
Posts: 9101
Premium Member
Re: If 2/z = 2/(z + 1) + 2/(z + 9) which of these integers could be the  [#permalink]

Show Tags

New post 19 Jul 2018, 14:56
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: If 2/z = 2/(z + 1) + 2/(z + 9) which of these integers could be the &nbs [#permalink] 19 Jul 2018, 14:56
Display posts from previous: Sort by

If 2/z = 2/(z + 1) + 2/(z + 9) which of these integers could be the

  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®.