Find all School-related info fast with the new School-Specific MBA Forum

 It is currently 04 May 2015, 07:13

### 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

# Is product 2*x*5*y an even integer? a.) 2 + x + 5 + y is an

Author Message
TAGS:
Current Student
Joined: 11 May 2008
Posts: 562
Followers: 7

Kudos [?]: 55 [0], given: 0

Is product 2*x*5*y an even integer? a.) 2 + x + 5 + y is an [#permalink]  02 Aug 2008, 02:17
Is product 2*x*5*y an even integer?

a.) 2 + x + 5 + y is an even integer
b.) x - y is an odd integer

pls give explanation...
Director
Joined: 27 May 2008
Posts: 550
Followers: 7

Kudos [?]: 209 [0], given: 0

Re: good one... [#permalink]  02 Aug 2008, 06:27
arjtryarjtry wrote:
Is product 2*x*5*y an even integer?

a.) 2 + x + 5 + y is an even integer
b.) x - y is an odd integer

pls give explanation...

2*x*5*y will be an even integer if x and y are integer .....

statement 1 : x+y+7 is even, x+y has to be odd so that odd + odd = even
x+y is odd, take x = 3.5 and y = 1.5 .... not suff
statement 2 : x-y is odd, take x = 3.5 and y = 0.5 ... not suff

combine m and n are positive integers.
x+y = 2m+1
x-y = 2n+1

x = m+n+1 ----> interger
y = m-n ---> integer

together suff... option C
VP
Joined: 17 Jun 2008
Posts: 1404
Followers: 7

Kudos [?]: 149 [0], given: 0

Re: good one... [#permalink]  02 Aug 2008, 10:28
arjtryarjtry wrote:
Is product 2*x*5*y an even integer?

a.) 2 + x + 5 + y is an even integer
b.) x - y is an odd integer

pls give explanation...

IMO D
Any number multiplied by 2 is even
hence irrespective of choices we can determine the answer
_________________

cheers
Its Now Or Never

VP
Joined: 17 Jun 2008
Posts: 1404
Followers: 7

Kudos [?]: 149 [0], given: 0

Re: good one... [#permalink]  02 Aug 2008, 10:37
spriya wrote:
arjtryarjtry wrote:
Is product 2*x*5*y an even integer?

a.) 2 + x + 5 + y is an even integer
b.) x - y is an odd integer

pls give explanation...

IMO D
Any number multiplied by 2 is even
hence irrespective of choices we can determine the answer

OOPS silly mistake i left out possibility of fractions
just occurred to me after seeing the posts

I would re analyse this problem :
consider (1) 2+x+y+5=n n is a even integer => x+y=n-7 => x,y can be fractions or integer => insufficient
consider (2) x-y=m m is odd integer
but here also x,y can be either integer or fraction => insufficient

now consider both (1) and (2) => 2x=m+n-7=> x=(m-7+n)/2 m-7 is even and n is even hence x is integer

also 2y= n-7-m => y=(n-7-m)/2 => m+7 is even n is even hence y is integer
=> 2*x*y*5 is even integer
hence (C) is IMO.
_________________

cheers
Its Now Or Never

Intern
Joined: 02 Aug 2008
Posts: 29
Followers: 0

Kudos [?]: 2 [0], given: 0

Re: good one... [#permalink]  02 Aug 2008, 22:37
removing the possibility of fractions was critical. this is how i did it, tell me if this sound good.

2+5+x+y = e
=> x+y = o
also given, x-y = o

adding the two, 2x must be o+o = even

if 2x is even, x must be integer. if x is integer, y is also integer, which means 10*x*y is even (ending with zero)

hence ans i C
Re: good one...   [#permalink] 02 Aug 2008, 22:37
Similar topics Replies Last post
Similar
Topics:
9 Is product 2*x*5*y an even integer? 13 22 Feb 2012, 06:33
7 Is product 2*x*5*y an even integer? 12 29 May 2009, 03:53
2 Is product 2*x*5*y an even integer? a. 2 + x + 5 + y is an 2 23 May 2008, 01:18
Is product 2*x*5*y an even integer? 1. 2 + x + 5 + y is an 5 02 Mar 2008, 03:22
Display posts from previous: Sort by