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

It is currently 17 Oct 2019, 16:00

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

If n is an integer, is n - 1 even?

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

Hide Tags

Find Similar Topics 
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 58402
If n is an integer, is n - 1 even?  [#permalink]

Show Tags

New post 06 Dec 2015, 12:09
00:00
A
B
C
D
E

Difficulty:

  5% (low)

Question Stats:

95% (00:41) correct 5% (01:25) wrong based on 159 sessions

HideShow timer Statistics

Verbal Forum Moderator
User avatar
V
Status: Greatness begins beyond your comfort zone
Joined: 08 Dec 2013
Posts: 2401
Location: India
Concentration: General Management, Strategy
Schools: Kelley '20, ISB '19
GPA: 3.2
WE: Information Technology (Consulting)
GMAT ToolKit User Reviews Badge CAT Tests
Re: If n is an integer, is n - 1 even?  [#permalink]

Show Tags

New post 06 Dec 2015, 12:16
(1) n - 2 is odd
n-1 = n-2 + 1
= Odd + 1
= Even

Sufficient.

(2) n + 1 is even
n+1=n+1-2
= even - 2
= even
Sufficient.

Answer D
_________________
When everything seems to be going against you, remember that the airplane takes off against the wind, not with it. - Henry Ford
The Moment You Think About Giving Up, Think Of The Reason Why You Held On So Long
Intern
Intern
avatar
Joined: 10 Sep 2015
Posts: 32
Re: If n is an integer, is n - 1 even?  [#permalink]

Show Tags

New post 08 Dec 2015, 08:39
n is integer, n-1 =even ?

1) n-2 is odd

n= odd +2 =odd
so, n is odd..

n-1 = even ( S)

2) n+1 = even
n= even-1
so, n = odd

therefore , n-1 = even (S)

D
Manager
Manager
avatar
B
Joined: 07 May 2015
Posts: 174
Location: India
GMAT 1: 660 Q48 V31
GPA: 3
GMAT ToolKit User
Re: If n is an integer, is n - 1 even?  [#permalink]

Show Tags

New post 09 Dec 2015, 09:01
n - 1 will be even if n is odd. Thus we need to prove is n is odd

(1) n - 2 is odd
odd-even = odd
Thus n = odd
Sufficient

(2) n + 1 is even
odd+odd= even
thus n is odd
Sufficient

Ans: D
Math Revolution GMAT Instructor
User avatar
V
Joined: 16 Aug 2015
Posts: 8009
GMAT 1: 760 Q51 V42
GPA: 3.82
Re: If n is an integer, is n - 1 even?  [#permalink]

Show Tags

New post 10 Dec 2015, 01:19
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.


3) If n is an integer, is n - 1 even?

(1) n - 2 is odd

(2) n + 1 is even


-> When you modify the original condition and question, it becomes n-1=even? --> n=even-1=odd?. There is 1 variable(n), which should match with the number of equations. So, 1 equation is needed. That is, for 1) 1 equation, for 2) 1 equation, which is likely to make D the answer.
1) n-2=odd, n=odd+2=odd -> yes, which is sufficient.
2) n+1=even, n=even-1=odd -> yes, which is sufficient.
Therefore, the answer is D.

* For cases where we need 1 more equation, such as original conditions with “1 variable”, or “2 variables and 1 equation”, or “3 variables and 2 equations”, we have 1 equation each in both 1) and 2). Therefore, there is 59 % chance that D is the answer, while A or B has 38% chance and C or E has 3% chance. Since D is most likely to be the answer using 1) and 2) separately according to DS definition. Obviously there may be cases where the answer is A, B, C or E.
_________________
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 $79 for 1 month Online Course"
"Free Resources-30 day online access & Diagnostic Test"
"Unlimited Access to over 120 free video lessons - try it yourself"
Current Student
User avatar
D
Joined: 12 Aug 2015
Posts: 2568
Schools: Boston U '20 (M)
GRE 1: Q169 V154
GMAT ToolKit User
Re: If n is an integer, is n - 1 even?  [#permalink]

Show Tags

New post 22 Aug 2016, 02:21
Current Student
User avatar
S
Status: Preparing for GMAT!!
Joined: 11 Oct 2015
Posts: 126
Location: India
Concentration: Entrepreneurship, International Business
GMAT 1: 660 Q47 V34
GMAT 2: 700 Q48 V38
GPA: 3.1
WE: General Management (Entertainment and Sports)
GMAT ToolKit User
Re: If n is an integer, is n - 1 even?  [#permalink]

Show Tags

New post 27 Dec 2016, 07:13
Bunuel wrote:
If n is an integer, is n - 1 even?

(1) n - 2 is odd

(2) n + 1 is even

1)
The consecutive number of n-2=odd is always even.
2)
The consecutive number of n+1=even, n is odd and n-1 is EVEN.

D
_________________
Yours,
Siva Rama Krishna Meka :)
GMAT Club Legend
GMAT Club Legend
User avatar
V
Joined: 12 Sep 2015
Posts: 4007
Location: Canada
Re: If n is an integer, is n - 1 even?  [#permalink]

Show Tags

New post 08 May 2018, 11:02
Top Contributor
Bunuel wrote:
If n is an integer, is n - 1 even?

(1) n - 2 is odd

(2) n + 1 is even


Some important rules:
1. ODD +/- ODD = EVEN
2. ODD +/- EVEN = ODD
3. EVEN +/- ODD = ODD
4. EVEN +/- EVEN = EVEN


Target question: Is n - 1 even?

Statement 1: n - 2 is odd
In other words, we can write n - 2 = ODD
Add 1 to both sides to get: n - 2 + 1 = ODD + 1
Simplify: n - 1 = ODD + 1
1 is ODD, so we can write: n - 1 = ODD + ODD
From rule #1, we can write: n - 1 = EVEN
So, the answer to the target question is YES, n-1 IS even
Since we can answer the target question with certainty, statement 1 is SUFFICIENT

Statement 2: n + 1 is even
In other words, we can write n + 1 = EVEN
Subtract 2 from to both sides to get: n + 1 - 2 = EVEN - 2
Simplify: n - 1 = EVEN - 2
2 is EVEN, so we can write: n - 1 = EVEN - EVEN
From rule #4, we can write: n - 1 = EVEN
So, the answer to the target question is YES, n-1 IS even
Since we can answer the target question with certainty, statement 2 is SUFFICIENT

Answer: D

Cheers,
Brent
_________________
Test confidently with gmatprepnow.com
Image
GMAT Club Bot
Re: If n is an integer, is n - 1 even?   [#permalink] 08 May 2018, 11:02
Display posts from previous: Sort by

If n is an integer, is n - 1 even?

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





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