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

It is currently 20 Oct 2019, 12:11

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

  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: 58434
If x is an even number, which of the following must be odd?  [#permalink]

Show Tags

New post 19 Feb 2018, 23:09
00:00
A
B
C
D
E

Difficulty:

  25% (medium)

Question Stats:

73% (01:01) correct 27% (00:53) wrong based on 85 sessions

HideShow timer Statistics

examPAL Representative
User avatar
P
Joined: 07 Dec 2017
Posts: 1153
If x is an even number, which of the following must be odd?  [#permalink]

Show Tags

New post Updated on: 22 Feb 2018, 09:50
1
Bunuel wrote:
If x is an even number, which of the following must be odd?

I. 3x + 1

II. (5x)^2 + 2

III. (x + 1)^2

(A) I only

(B) III only

(C) I and II only

(D) I and III only

(E) I, II, and III


Even/Odd questions are usually solvable without explicit calculations, using basic properties.
We'll look for such an answer, a Logical approach.

I. x is even --> 3x is odd*even=even --> 3x+1 is even + odd= odd
II. x is even --> 5x is odd*even=even --> (5x)^2 is even*even=even --> (5x)^2 + 2 is even+even=even
III. x is even --> x+1 is even+odd=odd --> (x+1)^2 is odd*odd=odd

(D) is our answer.
_________________

Originally posted by DavidTutorexamPAL on 20 Feb 2018, 00:08.
Last edited by DavidTutorexamPAL on 22 Feb 2018, 09:50, edited 1 time in total.
Manager
Manager
avatar
S
Joined: 18 Jul 2017
Posts: 57
CAT Tests
Re: If x is an even number, which of the following must be odd?  [#permalink]

Show Tags

New post 22 Feb 2018, 05:35
1
If x is an even number, which of the following must be odd?

I. 3x + 1

II. (5x)^2 + 2

III. (x + 1)^2

(A) I only

(B) III only

(C) I and II only

(D) I and III only

(E) I, II, and III


Lets substitute x=2,
1) 3(2) + 1 = 7 (ODD)
2) (5(2))^2 + 2 = 102 (Even)
3) (2+1)^2 = 9 (ODD)

So the option id D
Target Test Prep Representative
User avatar
G
Status: Head GMAT Instructor
Affiliations: Target Test Prep
Joined: 04 Mar 2011
Posts: 2815
Re: If x is an even number, which of the following must be odd?  [#permalink]

Show Tags

New post 22 Feb 2018, 09:23
Bunuel wrote:
If x is an even number, which of the following must be odd?

I. 3x + 1

II. (5x)^2 + 2

III. (x + 1)^2

(A) I only

(B) III only

(C) I and II only

(D) I and III only

(E) I, II, and III


We may recall that even + odd = odd and odd + even = odd.

I. 3x + 1

Since x is even, 3*(even) + 1 = even + odd = odd.

I is true.

II. (5x)^2 + 2

(5*(even))^2 + 2 = even + even = even

II is not true.

III. (x + 1)^2

(even + 1)^2 = (odd)^2 = odd

III is true.

Answer: D
_________________

Jeffrey Miller

Head of GMAT Instruction

Jeff@TargetTestPrep.com
TTP - Target Test Prep Logo
122 Reviews

5-star rated online GMAT quant
self study course

See why Target Test Prep is the top rated GMAT quant course on GMAT Club. Read Our Reviews

If you find one of my posts helpful, please take a moment to click on the "Kudos" button.

GMAT Club Bot
Re: If x is an even number, which of the following must be odd?   [#permalink] 22 Feb 2018, 09:23
Display posts from previous: Sort by

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

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





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