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

It is currently 21 Jul 2018, 06:52

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 odd number, which of the following must be even?

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

Hide Tags

Expert Post
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 47165
If n is an odd number, which of the following must be even?  [#permalink]

Show Tags

New post 13 Oct 2017, 00:02
00:00
A
B
C
D
E

Difficulty:

  15% (low)

Question Stats:

80% (00:48) correct 20% (00:27) wrong based on 82 sessions

HideShow timer Statistics

SC Moderator
avatar
D
Joined: 22 May 2016
Posts: 1833
Premium Member CAT Tests
If n is an odd number, which of the following must be even?  [#permalink]

Show Tags

New post 13 Oct 2017, 03:34
Bunuel wrote:
If n is an odd number, which of the following must be even?

A. (n - 1)/2

B. (n + 1)/2

C. n^2 + 2n

D. 2n + 2

E. 3n^2 - 2n

Use n = 1, n = 3, and in one case, n= 5

If n is odd, the most likely "must be even" expressions will have terms that are (Even)*(Odd) and/or (Odd + Odd).

Scanning the choices, "2n" in Answer D should stand out.

To guarantee that a term is even, we use 2n. 2 is even.
(Even) * (Even OR Odd) = Even.

Answer (D) 2n + 2
Even * Odd = Even, then
Even + Even = Even CORRECT

Nothing will make that expression odd. Examples:
n = 1: (2)(1) + 2 = (2 + 2) = 4
n = 3: (2)(3) + 2 = (6 + 2) = 8
n = -1: (2)(-1) + 2 = (-2+2) = 0

Checking the others:

A. (n - 1)/2
Division is unpredictable.
n = 1 yields result of 0, even.
BUT
If n = 3: (3-1)/2 =(2/2) = 1. REJECT

B. (n + 1)/2
Again, unpredictable.
n = 3: 4/2 = 2. Even. BUT
n = 5: 6/2 = 3. Odd. REJECT

C. n^2 + 2n
(Odd * Odd) = Odd, then
Odd + Even = Odd.

An odd number, squared, is always odd. 2n is even.
n = 1: (1 + 2) = 3. Odd. REJECT

E. 3n^2 - 2n
Odd * (Odd*Odd) = Odd, then
Odd - Even = Odd
n = 1: (3*1) - 2 = (3-2) = 1. REJECT

Answer
_________________

In the depths of winter, I finally learned
that within me there lay an invincible summer.

-- Albert Camus, "Return to Tipasa"

If n is an odd number, which of the following must be even? &nbs [#permalink] 13 Oct 2017, 03:34
Display posts from previous: Sort by

If n is an odd number, which of the following must be even?

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

Events & Promotions

PREV
NEXT


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®.