Is z an integer?

This topic has expert replies
Legendary Member
Posts: 1622
Joined: Thu Mar 01, 2018 7:22 am
Followed by:2 members

Is z an integer?

by Gmat_mission » Mon Jun 11, 2018 1:50 am

Timer

00:00

Your Answer

A

B

C

D

E

Global Stats

Is z an integer?

(1) 2z is an even number.

(2) 4z is an even number.

[spoiler]OA=A[/spoiler]

Why is sufficient the first statement but the second one isn't? I think both statements say almost the same. I need help here. Thanks in advance.

User avatar
GMAT Instructor
Posts: 15539
Joined: Tue May 25, 2010 12:04 pm
Location: New York, NY
Thanked: 13060 times
Followed by:1906 members
GMAT Score:790

by GMATGuruNY » Mon Jun 11, 2018 2:25 am

Timer

00:00

Your Answer

A

B

C

D

E

Global Stats

Gmat_mission wrote:Is z an integer?

(1) 2z is an even number.

(2) 4z is an even number.
Statement 1:
Options for 2z:
2z = 2, 4, 6, 8, 10, 12...
Dividing every value above by 2, we get the following options for z:
z = 1, 2, 3, 4, 5, 6...
In every case, z is an integer.
Thus, the answer to the question stem is YES.
SUFFICIENT.

Statement 2:
Options for 4z:
4z = 2, 4, 6, 8, 10, 12...
Dividing every value above by 4, we get the following options for z:
z = 1/2, 1, 3/2, 2, 5/2, 3...
If z = 1/2, then the answer to the questions stem is NO.
If z=1, then the answer to the question stem is YES.
Since the answer is NO in the first case but YES in the second case, INSUFFICIENT.

The correct answer is A.
Private tutor exclusively for the GMAT and GRE, with over 20 years of experience.
Followed here and elsewhere by over 1900 test-takers.
I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.

As a tutor, I don't simply teach you how I would approach problems.
I unlock the best way for YOU to solve problems.

For more information, please email me (Mitch Hunt) at [email protected].
Student Review #1
Student Review #2
Student Review #3