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Is z even? (1) 5z is even (2) 3z is even

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Manager
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Status: Current MBA Student
Joined: 19 Nov 2009
Posts: 99
Concentration: Finance, General Management
GMAT 1: 720 Q49 V40
Is z even? (1) 5z is even (2) 3z is even  [#permalink]

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New post 11 May 2011, 10:38
1
7
00:00
A
B
C
D
E

Difficulty:

  95% (hard)

Question Stats:

44% (00:58) correct 56% (00:30) wrong based on 196 sessions

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Is z even?

(1) 5z is even
(2) 3z is even
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Joined: 20 Dec 2010
Posts: 1810
Re: Even and odds problem  [#permalink]

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New post 11 May 2011, 11:30
3
1
tonebeeze wrote:
Is z even?

(1) 5z is even

z=2/5; 5z=2; z not even
z=2; 5z=10; z is even
Not Sufficient.

(2) 3z is even


z=2/3; 3z=2; z not even
z=2; 3z=6; z is even
Not Sufficient.

Combining both;
z can't be a fraction with denominator 3 or 5 because it has to satisfy both statements simultaneously.
Thus, z must be an even integer.
Sufficient.

Ans: "C"
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Re: Even and odds problem  [#permalink]

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New post 11 May 2011, 20:26
1
(1)
z = 2

z = 2/5

Not Sufficient

(2)

z = 2

z = 2/3

Not Sufficient

(1) + (2)

z = even

Answer - C
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Re: Even and odds problem  [#permalink]

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New post 11 May 2011, 20:40
So, Even number is an Integer considered.

a+b means z cant be divisible by 3/5 both.Hence C.
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Re: Is z even? (1) 5z is even (2) 3z is even  [#permalink]

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New post 03 Aug 2017, 11:37
1
tonebeeze wrote:
Is z even?

(1) 5z is even
(2) 3z is even


z = integers, decimals, fractions, etc.
z = even ?

1) 5z is even
z = \(\frac{2}{5}\)
5z = 2, but z ≠ even.
z = 2
5z = 10, and z = even.
2 different answers. Insufficient.

2) 3z = even
z = \(\frac{2}{3}\)
3z = 2, but z ≠ even
z = 2, 3z = 6
z = even
2 different answers. Insufficient.

1+2)

5z = even and 3z = even
3 and 5 are prime => z cannot be a fraction as it has to satisfy both the equations.
=> z has to be even.
Sufficient. C is the answer.
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Is z even? (1) 5z is even (2) 3z is even  [#permalink]

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New post 01 Nov 2018, 07:58
tonebeeze wrote:
Is z even?

(1) 5z is even
(2) 3z is even



(1) 5z is even
z=2, 5z is even yes
z=2/5 , 5z is even no
Insufficient.
(2) 3z is even
z=2, 3z is even yes
z=2/3 , 3z is even no
Insufficient.

Combining (1) and (2)
since even + even =even
Adding both (1) and (2)
5z+3z= even
or 8z=even
hence z could be odd or even.

hence answer should be E


Need an expert advice to analyse my logic.
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Re: Is z even? (1) 5z is even (2) 3z is even  [#permalink]

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New post 01 Nov 2018, 22:52
ritu1009 wrote:
tonebeeze wrote:
Is z even?

(1) 5z is even
(2) 3z is even



(1) 5z is even
z=2, 5z is even yes
z=2/5 , 5z is even no
Insufficient.
(2) 3z is even
z=2, 3z is even yes
z=2/3 , 3z is even no
Insufficient.

Combining (1) and (2)
since even + even =even
Adding both (1) and (2)
5z+3z= even
or 8z=even
hence z could be odd or even.

hence answer should be E


Need an expert advice to analyse my logic.


Instead adding you should have subtracted 3z from 5z:

5z - 3z = even -even = even;

2z = even;

z = even/2 = integer.

If z is an integer, then for 3z to be even z must be even too.
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Re: Is z even? (1) 5z is even (2) 3z is even &nbs [#permalink] 01 Nov 2018, 22:52
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