Is z an odd number?

Hi Ashikaverma13,

The best way to approach inequality questions of this type is to plug in values. There are two things you need to keep in mind while plugging in values on a Yes/No DS question

1. Plug in values to satisfy the statement first and then answer a Yes or No to the main question.
2. Plug in values to disprove the statement i.e. if you plug in a value which gives you a YES, try to plug in a value to get a NO instead of trying to get a definite YES or No and prove it sufficient

Also in questions where you are not given any constraint, you need to be doubly careful. Here we have not been given any information about the type of number z is. So z can be any real number. The trap here would be to assume that z has to be a positive integer.

Is z an odd number?

Keep in mind that only positive and negative numbers can be odd or even. We cannot have fractions or irrational numbers to be odd or even.

Statement 1 : 3z is an odd number

Plug in z = 1. This gives us a YES.
Plug in z =1/3. This gives us a NO. Insufficient.

Statement 2 : z/3 is an odd number

z/3 = odd -----> z = odd * 3 -----> z = odd. Sufficient.

OA : B

CrackVerbal Academics Team

IMO: B
Explanation:

Statement 1 : 3z is an odd number


for z = 1. YES.
for z = 7/3. NO.
Insufficient.

Statement 2 : z/3 is an odd number

z/3 = odd
odd * 3 = odd
Therefore, z = odd.
Sufficient.

Thus, answer is B

Can you please explain statement 1 again. As far as I know Odd*odd =odd.. now it is mentioned 3z=odd
so 3 is odd so for 3z to be odd z has to be odd

Yes, odd*odd = odd but we don't know whether z is an integer thus from 3z = odd it follows that z = odd/3. So, z can be 1/3, 3/3=1, 5/3, 7/3, 9/3=3, ..., -1/3, ...
_________________

Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________