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

Question

Is z even?

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

fluke · Accepted Answer

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"

subhashghosh · Answer

(1)
z = 2

z = 2/5

Not Sufficient

(2)

z = 2

z = 2/3

Not Sufficient

(1) + (2)

z = even

Answer - C

amit2k9 · Answer

So, Even number is an Integer considered.

a+b means z cant be divisible by 3/5 both.Hence C.

akshayk · Answer

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.

ritu1009 · Answer

(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.

Bunuel · Answer

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.

Archit3110 · Answer

#1
5z is even 
z= 2 or 2/5
insufficient
#2
3z is even
z=2 or 2/3
insufficient
from 1 &2
z=2 or even integer only 
IMO C

CEdward · Answer

So I chose C too, but I wasn't firm about whether z could not be a fraction. Is this strictly trial and error?

chetan2u · Answer

Remember:  z is not given as integer

(1) 5z is even
Even numbers are of type 2, so 5z=2x..... z=\frac{2}{5}x , where x is an integer.
If x= 1, then z=2/5, but if x=5, then z=2
 Thus, 5z is even when z is even integer or when z has even numerator and 5 in denominator in its simplest form 
Insuff

(2) 3z is even
Even numbers are of type 2y, so 3z=2y..... z=\frac{2}{3}y , where y is an integer.
If x= 1, then z=2/3, but if x=3, then z=2
 Thus, 3z is even when z is even integer or when z has even numerator and 3 in denominator in its simplest form 
Insuff

Combined
 z is even integer  is common in the two statements.
Thus, sufficient

C

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

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GMAT Data Sufficiency (DS) Questions

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

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