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Is Z an odd integer? (1) Z/3 is odd. (2) 3Z is odd
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01 May 2007, 00:09
Is Z an odd integer?
(1) Z/3 is odd.
(2) 3Z is odd. == Message from GMAT Club Team == This is not a quality discussion. It has been retired. If you would like to discuss this question please repost 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.



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Re: Fractions
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01 May 2007, 00:41
Juaz wrote: Is Z an odd integer?
(1) Z/3 is odd. (2) 3Z is odd.
1> z/3 is odd i.e z=3(n) and z/n=3(n)/3=n and that is equal to odd . And hence Z=odd. So sufficient.
2> 3z is odd only when z is odd (odd * odd= odd) and hence sufficient.
So answere is D.
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Re: Fractions
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01 May 2007, 01:18
Juaz wrote: Is Z an odd integer?
(1) Z/3 is odd. (2) 3Z is odd.
(1) Sufficient
If Z=9 then 9/3 is odd
If Z=6 then 6/3 is even
(2) Sufficient
If Z=2 then 3*2 is even
If Z=3 then 3*3 is odd
Answer D.



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I think the answer is E
Even with statements 1 and 2 together, we can never know if Z is actually an integer.



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Re: Fractions
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01 May 2007, 02:02
Juaz wrote: Is Z an odd integer?
(1) Z/3 is odd. (2) 3Z is odd.
(1) z/3 is an odd integer, so we can write z/3=k for some odd integer k
Thus z=3k, which is an odd integer. SUFF
(2) 3z is an odd integer m. Thus z=m/3. If m is a multiple of 3, z is an odd integer. However, if m is not a multiple of 3, z will not be an integer.
NOT SUFF
A



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Updated on: 01 May 2007, 02:05
(A) for me
From 1
z/3 = 2*k+1 where k is an integer
<=> z = 3*(2*k + 1) = ODD*ODD = ODD
SUFF.
From 2
3*z = 2*k+1
<=> z= (2*k+1)/3
So,
o If 2*k+1 = 3*n (n an ODD integer), then:
z = 3*n / 3 and z is an ODD
o If 2*k+1 is not a multiple of 3, then:
z is even not an integer.
INSUFF.
Originally posted by Fig on 01 May 2007, 02:02.
Last edited by Fig on 01 May 2007, 02:05, edited 1 time in total.



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St1:
Testing some values... z is 9, z/3 is odd. z is 15, z/3 is odd... etc
Sufficient.
St2:
odd * z = odd
z must be odd. Sufficient.
Ans D



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ywilfred wrote: St1: Testing some values... z is 9, z/3 is odd. z is 15, z/3 is odd... etc Sufficient.
St2: odd * z = odd
z must be odd. Sufficient.
Ans D
In 2, try z=1/3 ... We have 3*z = ODD



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Re: Fractions
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01 May 2007, 02:23
Juaz wrote: Is Z an odd integer?
(1) Z/3 is odd. (2) 3Z is odd.
if u simply appy 5/3 u can figure out d is not the answer
the answer is E



Director
Joined: 12 Jun 2006
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Going for A
Quote: Even with statements 1 and 2 together, we can never know if Z is actually an integer.
is there such a thing as an odd or even fraction? And if so, are there odd/even fractions at the level of math we're dealing with. If not, A must be suff



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Updated on: 01 May 2007, 11:27
No, odds and evens are only for integers. While the question asks about whether Z is odd, statements 1 and 2 gives clue some fractions that contain z.
Statemnet 1 confirms that Z is indeed an integer, while statement 2 does not neccessarily indicate that Z is an integer, regardless whether odd or even.
My updated Answer: A
Originally posted by Mishari on 01 May 2007, 06:30.
Last edited by Mishari on 01 May 2007, 11:27, edited 1 time in total.



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Re: Fractions
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01 May 2007, 07:09
kevincan wrote: Juaz wrote: Is Z an odd integer?
(1) Z/3 is odd. (2) 3Z is odd. (1) z/3 is an odd integer, so we can write z/3=k for some odd integer k Thus z=3k, which is an odd integer. SUFF (2) 3z is an odd integer m. Thus z=m/3. If m is a multiple of 3, z is an odd integer. However, if m is not a multiple of 3, z will not be an integer. NOT SUFF A
Hi kevin,
Can you elaborate on why statement 2 is insufficient..?
Javed.
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Re: Fractions
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01 May 2007, 08:12
Juaz wrote: Is Z an odd integer?
(1) Z/3 is odd. (2) 3Z is odd.
Crazy...it's like playing word games. Is Z odd AND integer?
(1) Z/3=Odd > Z=3*Odd > Z=Odd*Odd, so Z must be Odd. SUFF.
(2) 3Z=Odd > Z=Odd/3. So Z could be 7/3 or 15/3, one is integer another one isn't. Or you can look at it as 3*(5)=Odd (yes, Z is an odd integer); but 3*(1/3) = Odd (no, Z is neither odd nor an integer). ___
So the answer is A I guess.



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Re: Fractions
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01 May 2007, 08:34
[quote="Juaz"]Is Z an odd integer?
(1) Z/3 is odd.
(2) 3Z is odd.[/quote]
A
stmt 1)
z must be ODD and multiple of 3 (it's not possible to have fractions because the condition would not be satisfied)
> Sufficient
stmt 2)
if z=5/3 then 3*z=3*5/3=5 the condition is satisfied but z is not an integer
if z=5 then 3*z=3*5=15 the condition is satisfied and z is an odd integer
> Insufficient



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OA is A.
Thanks guys!!



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Re: Is Z an odd integer? (1) Z/3 is odd. (2) 3Z is odd
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08 Jan 2018, 02:13
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Re: Is Z an odd integer? (1) Z/3 is odd. (2) 3Z is odd &nbs
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08 Jan 2018, 02:13






