Data Sufficiency

sukhman wrote:Is z even?

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

Target question: Is z even?

Statement 1: z/2 is even
NOTE: When we say that a number is even, we are also saying that the number is an integer.
So, if z/2 is even, then z/2 = some integer.
From this, we can conclude that z = 2(some integer), which means z must be even
Since we can answer the target question with certainty, statement 1 is SUFFICIENT

Statement 2: 3z is even.
There are several values of z that satisfy this condition. Here are two:
Case a: z = 2, in which case 3z = 6, which is even. Here, z is even
Case b: z = 2/3, in which case 3z = 2, which is even. Here, z is not an integer, so z is not even
Since we cannot answer the target question with certainty, statement 2 is NOT SUFFICIENT

Answer = A

Cheers,
Brent