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Director
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Ds Odd even number [#permalink]
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04 Aug 2004, 02:35
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Hi all, what is your answer to this?
Is Y even?
(1) 2Y is even.
(2) Y^2 is even.
Last edited by saurya_s on 04 Aug 2004, 03:12, edited 1 time in total.



Director
Joined: 08 Jul 2004
Posts: 596

Hi bigtooth
I meant Y square in choice 2. I have corrected that. can you explain your answer.



Senior Manager
Affiliations: CFA Level 2
Joined: 05 May 2004
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Location: Hanoi

Ok. See, odd x odd = odd
even x even = even
From (2) you have Y^2 = even means Y x Y = even. There's only one possibility for Y x Y = even when Y is even. Hope it is clear enough.
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Senior Manager
Joined: 19 May 2004
Posts: 291

I would pick C here.
1) Insufficient  obvious.
2) What about Y=sqrt(2) ?
1+2) sufficient.



Manager
Joined: 19 Jun 2003
Posts: 151

Dookie wrote: I would pick C here.
1) Insufficient  obvious. 2) What about Y=sqrt(2) ?
1+2) sufficient.
hmmm..good point
so then from (1), we get 2.sqrt(2). This is not an integer. So you are conluding that Y is not even because it is not an integer.
I'd have chosen B, but Dookie is right, question does not mention whether Y is integer. So B would be wrong.



Senior Manager
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Yeah, you'r right Dookie. I just want to kick myself
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GMAT Club Legend
Joined: 07 Jul 2004
Posts: 5043
Location: Singapore

Statement 1
2Y = even
Y = even/2
Any even number divided by 2 has to be even. So (1) is sufficient
Statement2
Y^2 = even
In order for Y^2 to be even, Y has to even. So (2) is also sufficient.
A way to test is to take some arbitary numbers:
If Y is even  0,2,4,6,8,10..
Y^2 is even  0,4,16,36,64,100...
If Y i odd  1,3,5,7,9,11...
Y^2 is odd  1,9,25,49,121...
So answer is (D), both statements on their own are sufficient.



Director
Joined: 20 Jul 2004
Posts: 592

C?
Is Y even?
(1) 2Y is even.
2Y = 4 shows Y = 2(even)
2Y = 6 shows Y = 3(odd)
Not sufficient.
(2) Y^2 is even.
Y^2 = 2 shows Y = sqrt(2) (not even)
Y^2 = 4 gives Y = 2 (even)
Not sufficient.
(3) together
taking both statements will exclude choices like Y = 3 or sqrt(2) from above. 2 satisfies both statements and ans to the question is "Yes, Y is even".



GMAT Club Legend
Joined: 07 Jul 2004
Posts: 5043
Location: Singapore

Good catch, hardworker ! Statement 2 should be insufficient while statmenet 1 is sufficient. In this repsect, it should be A since the gmat states that C is "both statements are sufficient while neither one is"



Manager
Joined: 28 Jul 2004
Posts: 179

i understand each statements is insufficient alone. Fine....
Put togather we cannot say whether Y is even, because even after we put these two togather, we have the same problem as they individually had.
I prefer a E to this question. what is the OA ? please



Director
Joined: 20 Jul 2004
Posts: 592

ywilfred wrote: Statement 1 2Y = even Y = even/2
Any even number divided by 2 has to be even. So (1) is sufficient
ywilfred, I still think (1) is not sufficient by itself.
Nevetheless, I dont agree with "Any even number divided by 2 has to be even. "
6 is an even number. This when divided by 2 gives 3, which is not even.










