It is currently 22 Mar 2018, 14:49

### 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

# Even-odd numbers

Author Message
Manager
Joined: 11 Apr 2009
Posts: 157

### Show Tags

20 May 2009, 17:42
00:00

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct 100% (00:00) wrong based on 2 sessions

### HideShow timer Statistics

If a , b, and c are integers and $$\frac{ab^2}{c}$$ is a positive even integer, which of the following must
be true?

I. ab is even
II. ab > 0
III. c is even

I only
II only
I and II
I and III
I, II, and III

--== Message from GMAT Club Team ==--

This is not a quality discussion. It has been retired.

If you would like to discuss this question please re-post it in the respective forum. Thank you!

To review the GMAT Club's Forums Posting Guidelines, please follow these links: Quantitative | Verbal Please note - we may remove posts that do not follow our posting guidelines. Thank you.
Director
Joined: 23 May 2008
Posts: 757

### Show Tags

20 May 2009, 18:32
II only

example

a=3, b=3, c=3

3(3^2)/3

ab= (3x3) is not even and c=(3) is not even
Manager
Joined: 11 Apr 2009
Posts: 157

### Show Tags

20 May 2009, 18:46
If a=b=c=3 then ab^2/c will not be an even positive integer.

How do I choose the right numbers?
Intern
Joined: 02 Mar 2009
Posts: 43
Location: Austin

### Show Tags

20 May 2009, 19:43
A.

ab has to be even for ab^2/c to be even. Rest need not be true.
Manager
Joined: 14 May 2009
Posts: 189

### Show Tags

26 May 2009, 00:11
c doesn't have to be even, as b can be 3 and c can be 3, and a is even.

ab>0, not necessarily true. we could have a<0 b>0 and c<0, in which case ab/c >0 but ab<0.

Only ab has to be even, because if it weren't, that means it doesn't have a multiple of 2, and since c is a factor of ab, neither does c.
_________________

Manager
Joined: 08 Apr 2009
Posts: 96

### Show Tags

26 May 2009, 10:54
IMO- II only
Whats the OA?
Manager
Joined: 14 May 2009
Posts: 189

### Show Tags

26 May 2009, 11:02
chill wrote:
IMO- II only
Whats the OA?

a=-1
b=1
c=-1

ab^2/c>0 but ab<0 ..........
_________________

Senior Manager
Joined: 08 Jan 2009
Posts: 317

### Show Tags

26 May 2009, 23:04
a,b,c are integers

(a * b * b) / c = +ve ( even)

From this we know that when the numerator is odd then we will not get a +ve ( even) integer.
So the numerator needs to be even.
So either a or b need to be even so ab is even.

Other two are not true.
Manager
Joined: 10 Aug 2008
Posts: 73

### Show Tags

27 May 2009, 08:36
ab^2/c = ab*b/c

lets assume a =1, b=2 than 4/c in this case ab = 2 (even)

But if c = 4 than a*b*b/c = 1 & this is not +ve even number

So I only is not true.

ab >0 does not conclude anything, see the above example.

So II only is not true

Now come of 3rd statement c is even. Again in the above example c is even but still ab62/c is not even .

So III only is also not sufficient.

And also No Other combination of I, II & III .

For me this question is Inconclusive.
SVP
Joined: 29 Aug 2007
Posts: 2453

### Show Tags

27 May 2009, 08:57
gmatprep09 wrote:
If a , b, and c are integers and ab^2/c is a positive even integer, which of the following must be true?

I. ab is even
II. ab > 0
III. c is even

I only
II only
I and II
I and III
I, II, and III

ab^2/c = 2k where k is any +ve integer.

I. ab is even - true: Since 2k is even, either of a or b must be even. Any odd (if ab^2 is odd) divided by any integer (c must be odd) never results in even. So either a or b must be even.

II. ab > 0 - Not true: If a and c are +ve, and b is -ve, 2k is +ve and ab 0.

III. c is even - Not true: If a = 5, b = 4 and c = 1, 2k is even. If a = 4, b = 4 and c = 4, 2k is even. So C is not necessarily an even.

Only I is correct.

--== Message from GMAT Club Team ==--

This is not a quality discussion. It has been retired.

If you would like to discuss this question please re-post it in the respective forum. Thank you!

To review the GMAT Club's Forums Posting Guidelines, please follow these links: Quantitative | Verbal Please note - we may remove posts that do not follow our posting guidelines. Thank you.

_________________

Gmat: http://gmatclub.com/forum/everything-you-need-to-prepare-for-the-gmat-revised-77983.html

GT

Re: Even-odd numbers   [#permalink] 27 May 2009, 08:57
Display posts from previous: Sort by