Integers

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aks135: Newbie | Next Rank: 10 Posts; Posts: 3; Joined: Mon Jun 15, 2009 8:58 pm

by aks135 » Wed Jun 17, 2009 1:44 am

If x,y and z are integers, is x+y+2z even?
a) x+z is even
b) y+z is even

[spoiler]OA: C[/spoiler]

Can someone please explain why?[/spoiler]

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Source: Beat The GMAT — Data Sufficiency | Wed Jun 17, 2009 1:44 am

tohellandback: Legendary Member; Posts: 752; Joined: Sun May 17, 2009 11:04 pm; Location: Tokyo; Thanked: 81 times; GMAT Score:680

Re: Integers

by tohellandback » Wed Jun 17, 2009 1:52 am

aks135 wrote:If x,y and z are integers, is x+y+2z even?
a) x+z is even
b) y+z is even

[spoiler]OA: C[/spoiler]

Can someone please explain why?[/spoiler]

C because
a)x+z=even
x+y+2z=(x+z)+(y+z) we need to know whether y+z is even or odd
NOT SUFFICIENT

b) same as above- not sufficient

combine both
(x+z)+(y+z)=even +even=even

The powers of two are bloody impolite!!

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