It is currently 20 Feb 2018, 22:53

### 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

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

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# How many odd factors does 210 have?

Author Message
TAGS:

### Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 43834
How many odd factors does 210 have? [#permalink]

### Show Tags

24 Feb 2015, 06:54
1
KUDOS
Expert's post
3
This post was
BOOKMARKED
00:00

Difficulty:

35% (medium)

Question Stats:

58% (00:35) correct 42% (00:32) wrong based on 247 sessions

### HideShow timer Statistics

How many odd factors does 210 have?

(A) 3
(B) 4
(C) 5
(D) 6
(E) 8

Kudos for a correct solution.
[Reveal] Spoiler: OA

_________________
Manager
Joined: 14 Sep 2014
Posts: 106
Concentration: Technology, Finance
WE: Analyst (Other)
Re: How many odd factors does 210 have? [#permalink]

### Show Tags

24 Feb 2015, 07:00
1
KUDOS
Making a factor pair table:

1 * 210
2 * 105
3 * 70
5 * 42
6 * 35
7 * 30
10 * 21
14 * 15

There are eight pairs and each pair has one odd factor.
Intern
Joined: 01 Feb 2015
Posts: 23
Location: United States (CA)
Concentration: Real Estate
GMAT 1: 680 Q44 V38
GMAT 2: 740 Q49 V42
GPA: 3.45
WE: Project Management (Other)
Re: How many odd factors does 210 have? [#permalink]

### Show Tags

24 Feb 2015, 07:45
1
KUDOS
IMO E

210=1*2*3*5*7
can be expanded to 1,3, 5, 7, 15 ,21, 35, 105 }8 unique odd factors
Intern
Joined: 13 Aug 2013
Posts: 45
How many odd factors does 210 have? [#permalink]

### Show Tags

24 Feb 2015, 07:55
3
KUDOS
1
This post was
BOOKMARKED
IMO E

Factors of 210 = 2 x 3 x 5 x 7.
Apart from 2, all remaining factors are odd and will produce odd results. So basically now the question becomes, find the number of factors of (3 x 5 x 7).

Using the formula we straight away get 8. No need to list down the factors at all!
_________________

Kudos plz if it helped

Last edited by rockstar23 on 26 Feb 2015, 09:24, edited 1 time in total.
Math Expert
Joined: 02 Aug 2009
Posts: 5658
Re: How many odd factors does 210 have? [#permalink]

### Show Tags

24 Feb 2015, 08:06
2
KUDOS
Expert's post
Bunuel wrote:
How many odd factors does 210 have?

(A) 3
(B) 4
(C) 5
(D) 6
(E) 8

Kudos for a correct solution.

ans 8...E
210= 2*3*5*7...
number of odd factors will be without 2.. so number of factors=(1+1)*(1+1)*(1+1)=8
_________________

Absolute modulus :http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372
Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html

BANGALORE/-

SVP
Status: The Best Or Nothing
Joined: 27 Dec 2012
Posts: 1839
Location: India
Concentration: General Management, Technology
WE: Information Technology (Computer Software)
Re: How many odd factors does 210 have? [#permalink]

### Show Tags

24 Feb 2015, 20:19
1
KUDOS

$$210 = 2^1 * 3^1 * 5^1 * 7^1$$

Total factors = (1+1)(1+1)(1+1)(1+1) = 16

$$Odd factors = 2^3 = 8$$
_________________

Kindly press "+1 Kudos" to appreciate

EMPOWERgmat Instructor
Status: GMAT Assassin/Co-Founder
Affiliations: EMPOWERgmat
Joined: 19 Dec 2014
Posts: 11046
Location: United States (CA)
GMAT 1: 800 Q51 V49
GRE 1: 340 Q170 V170
Re: How many odd factors does 210 have? [#permalink]

### Show Tags

24 Feb 2015, 22:19
rockstar23 wrote:
IMO D

Factors of 210 = 2 x 3 x 5 x 7.
Apart from 2, all remaining factors are odd and will produce odd results. So basically now the question becomes, find the number of factors of (3 x 5 x 7).

Using the formula we straight away get 8. No need to list down the factors at all!

Hi rockstar23,

Your approach is correct, but you've listed the wrong answer. A minor point, but an important one.

GMAT assassins aren't born, they're made,
Rich
_________________

760+: Learn What GMAT Assassins Do to Score at the Highest Levels
Contact Rich at: Rich.C@empowergmat.com

# Rich Cohen

Co-Founder & GMAT Assassin

Special Offer: Save $75 + GMAT Club Tests Free Official GMAT Exam Packs + 70 Pt. Improvement Guarantee www.empowergmat.com/ ***********************Select EMPOWERgmat Courses now include ALL 6 Official GMAC CATs!*********************** Senior Manager Joined: 27 Oct 2013 Posts: 252 Location: India Concentration: General Management, Technology GMAT Date: 03-02-2015 GPA: 3.88 Re: How many odd factors does 210 have? [#permalink] ### Show Tags 25 Feb 2015, 00:56 3 This post received KUDOS Here we go: 210 = 2 * 3 * 5 * 7 Odd factors(exclude 2) = 3^1 * 5^1 * 7^1 =====> (1+1) * (1+1) * (1+1) ----> 2 * 2 * 2 = 8 option E is correct To add ----> If someone is interested in finding out the number of even factors ---> {Total factor} - {Odd Factors} ---> 16 - 8 = 8 SVP Joined: 06 Nov 2014 Posts: 1904 Re: How many odd factors does 210 have? [#permalink] ### Show Tags 28 Feb 2015, 06:00 1 This post received KUDOS Bunuel wrote: How many odd factors does 210 have? (A) 3 (B) 4 (C) 5 (D) 6 (E) 8 Kudos for a correct solution. 210 = 2^1 * 3^1 * 5^1 * 7^1 We can see that all are odd numbers except 2. Multiplication with an even number yields an even number. Total factors = (1+1)(1+1)(1+1)(1+1) = 16 Out of these we only need to consider factors of 3,5, and 7 = (1+1)(1+1)(1+1) = 8 Hence option E. -- Optimus Prep's GMAT On Demand course for only$299 covers all verbal and quant. concepts in detail. Visit the following link to get your 7 days free trial account: http://www.optimus-prep.com/gmat-on-demand-course
Math Expert
Joined: 02 Sep 2009
Posts: 43834
Re: How many odd factors does 210 have? [#permalink]

### Show Tags

02 Mar 2015, 05:27
Expert's post
1
This post was
BOOKMARKED
Bunuel wrote:
How many odd factors does 210 have?

(A) 3
(B) 4
(C) 5
(D) 6
(E) 8

Kudos for a correct solution.

MAGOOSH OFFICIAL SOLUTION:

For odd factors, we put aside the factor of two, and look at the other prime factors.
set of exponents = {1, 1, 1}
plus 1 to each = {2, 2, 2}
product = 2*2*2 = 8

Therefore, there are 8 odd factors of 210. In case you are curious, they are {1, 3, 5, 7, 15, 21, 35, and 105}

_________________
Current Student
Joined: 18 Oct 2014
Posts: 902
Location: United States
GMAT 1: 660 Q49 V31
GPA: 3.98
Re: How many odd factors does 210 have? [#permalink]

### Show Tags

04 Jun 2016, 07:07
Bunuel wrote:
How many odd factors does 210 have?

(A) 3
(B) 4
(C) 5
(D) 6
(E) 8

Kudos for a correct solution.

Opting out even factors from total number of factors will give total odd factors.

factors of 210= 5*2*7*3

If we do not consider factors of 2, we will get total odd factors= (1+1)(1+1)(1+1)= 2*2*2= 8
_________________

I welcome critical analysis of my post!! That will help me reach 700+

Director
Joined: 02 Sep 2016
Posts: 786
Re: How many odd factors does 210 have? [#permalink]

### Show Tags

03 Sep 2017, 02:55
Any integer * Even integer = Even integer

Therefore we do not calculate number of factors of 2.

3^1*7*1*5*1

= (2*2*2)
=8
_________________

Help me make my explanation better by providing a logical feedback.

If you liked the post, HIT KUDOS !!

Don't quit.............Do it.

Re: How many odd factors does 210 have?   [#permalink] 03 Sep 2017, 02:55
Display posts from previous: Sort by