simplyjat wrote:This is a question for mgmat. For which I do not agree with the explanation. What do you guys say...
Is z even?
(1) z/2 is even.
(2) 3z is even.
Moderator, if it is not OK to post mgat questions here, kindly delete the post.
(1) z/2 = even
Like any other equation, we can manipulate this to:
z = 2*even
Well, 2 times any integer will be even, therefore z will always be even: sufficient.
(2) 3z = even.
z = even/3
Will all even numbers divided by 3 be even? No. Will some of them be even? yes.
For example, we could have picked:
z = 6/3 = 2. Is 2 even? Yes.
or
z = 4/3 = 1.333. Is 1.333 even? No.
Since we can get a "yes" and a "no" answer, (2) is insufficient.
(1) is sufficient, (2) is insufficient: choose (A).
* * *
If you chose (D), both sufficient, you probably made the erroneous assumption that z had to be an integer. However, since we're never told that z must be an integer, we can't preclude other possibilities.
