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

It is currently 10 Dec 2018, 00:44

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.

M60-15

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

Hide Tags

Math Revolution GMAT Instructor
User avatar
V
Joined: 16 Aug 2015
Posts: 6613
GMAT 1: 760 Q51 V42
GPA: 3.82
Premium Member
M60-15  [#permalink]

Show Tags

New post 11 Jun 2018, 05:26
00:00
A
B
C
D
E

Difficulty:

  35% (medium)

Question Stats:

75% (00:41) correct 25% (00:01) wrong based on 8 sessions

HideShow timer Statistics

If x, y, and z are positive integers, is x+y divisible by 2?

1) x+z is divisible by 2

2) y+z is divisible by 2

_________________

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 $99 for 3 month Online Course"
"Free Resources-30 day online access & Diagnostic Test"
"Unlimited Access to over 120 free video lessons - try it yourself"

Math Revolution GMAT Instructor
User avatar
V
Joined: 16 Aug 2015
Posts: 6613
GMAT 1: 760 Q51 V42
GPA: 3.82
Premium Member
Re M60-15  [#permalink]

Show Tags

New post 11 Jun 2018, 05:26
Official Solution:



Forget conventional ways of solving math questions. For DS problems, the VA (Variable Approach) method is the quickest and easiest way to find the answer without actually solving the problem. Remember that equal numbers of variables and independent equations ensure a solution.



Since we have 3 variables (x, y and z) and 0 equations, E is most likely to be the answer. So, we should consider conditions 1) and 2) together first.



Conditions 1) and 2):

There are two cases to consider.

Case 1: If x, y, and z are all even, then the answer is 'yes'

Case 2: If x, y, and z are all odd, then the answer is also 'yes'

Since no other cases are possible, both conditions are sufficient, when taken together.



Since this is an integer question (one of the key question areas), CMT

(Common Mistake Type) 4(A) of the VA (Variable Approach) method tells us that we should also check answers A and B.



Condition 1)

Since it tells us nothing about y, condition 1) is not sufficient.



Condition 2)

Since it tells us nothing about y, condition 2) is not sufficient.



Therefore, C is the answer.



Normally, in problems which require 2 equations, such as those in which the original conditions include 2 variables, or 3 variables and 1 equation, or 4 variables and 2 equations, each of conditions 1) and 2) provide an additional equation. In these problems, the two key possibilities are that C is the answer (with probability 70%), and E is the answer (with probability 25%). Thus, there is only a 5% chance that A, B or D is the answer. This occurs in common mistake types 3 and 4. Since C (both conditions together are sufficient) is the most likely answer, we save time by first checking whether conditions 1) and 2) are sufficient, when taken together. Obviously, there may be cases in which the answer is A, B, D or E, but if conditions 1) and 2) are NOT sufficient when taken together, the answer must be E.



Answer: C
_________________

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 $99 for 3 month Online Course"
"Free Resources-30 day online access & Diagnostic Test"
"Unlimited Access to over 120 free video lessons - try it yourself"

Intern
Intern
avatar
B
Joined: 01 Apr 2018
Posts: 6
Re: M60-15  [#permalink]

Show Tags

New post 13 Sep 2018, 06:06
Can someone please Explain How both the statements taken together are sufficient since from the equations 1 and 2 we get they are either odd or even but we are not sure if they are even or odd , right??
Intern
Intern
avatar
B
Joined: 02 Jul 2018
Posts: 4
CAT Tests
Re: M60-15  [#permalink]

Show Tags

New post 29 Sep 2018, 18:04
Anirudh134 wrote:
Can someone please Explain How both the statements taken together are sufficient since from the equations 1 and 2 we get they are either odd or even but we are not sure if they are even or odd , right??


From equation 1 & 2, we determine either x, y, z are all even OR are all odd. I think you got it till there.

In both the cases (all even or all odd), if you try calculating x+y/2, we can conclude that it is divisible by 2. Hence sufficient.
Director
Director
User avatar
P
Joined: 08 Jun 2013
Posts: 514
Location: India
Schools: INSEAD Jan '19
GMAT 1: 200 Q1 V1
GPA: 3.82
WE: Engineering (Other)
GMAT ToolKit User Premium Member
Re: M60-15  [#permalink]

Show Tags

New post 29 Sep 2018, 18:34
Anirudh134 wrote:
Can someone please Explain How both the statements taken together are sufficient since from the equations 1 and 2 we get they are either odd or even but we are not sure if they are even or odd , right??


Anirudh134

If x, y, and z are positive integers, is x+y divisible by 2?

1) x+z is divisible by 2

2) y+z is divisible by 2

ST : 1 ) gives

X+Z is even number.

even + even = even or odd + odd = odd.

so both X and Z are either even or odd.

Question - Is X + Y even ? We can not tell at this point. Not sufficient.

Now ST : 2 ) gives

Y+Z is even number.

again even + even = even or odd + odd = odd.

so both Y and Z are either even or odd.

Question - Is X + Y even ? We can not tell this from only statement 2. Not sufficient.


Taking St-1 and St-2 together

Case I) - If from St-1 X and Z both even then Y and Z also even. All X, Y and Z even.

So X + Y even - Sufficient.

Case II) - If from St-1 X and Z both odd then Y and Z also odd. All X, Y and Z odd.

So X + Y = Odd + Odd = Even - Sufficient.

Does this help?
_________________

It seems Kudos button not working correctly with all my posts...

Please check if it is working with this post......

is it?....

Anyways...Thanks for trying :cool:

GMAT Club Bot
Re: M60-15 &nbs [#permalink] 29 Sep 2018, 18:34
Display posts from previous: Sort by

M60-15

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

Moderators: chetan2u, Bunuel



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®.