If w, x and y are different positive integers, and wxy =...

This topic has expert replies
User avatar
Master | Next Rank: 500 Posts
Posts: 155
Joined: Mon Dec 13, 2010 11:02 am
Thanked: 3 times
If w, x and y are different positive integers, and wxy = 24, is xy divisible by 6?

(1) wy is not divisible by 6.

(2) x is even.

Solution by author:


Image

Author just came up with "good" examples (counter cases) in BOTH cases. Good because both ARE SAME. How I indistinctly come up with them? [/img]
People are not prisoners of fate, but prisoners of their own mind.

User avatar
Master | Next Rank: 500 Posts
Posts: 155
Joined: Mon Dec 13, 2010 11:02 am
Thanked: 3 times

by towerSpider » Wed Mar 25, 2015 6:55 am
And I think it is "good" also because the author came up with way too fast. Any input? Thanks.
People are not prisoners of fate, but prisoners of their own mind.

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 » Wed Mar 25, 2015 7:16 am
towerSpider wrote:If w, x and y are different positive integers, and wxy = 24, is xy divisible by 6?

(1) wy is not divisible by 6.

(2) x is even.
List combinations of 3 distinct positive integers with a product of 24:
1*2*12.
1*3*8
1*4*6
2*3*4.

Statement 1: wy is not divisible by 6
Case 1: w=1 and y=2, implying that x=12.
In this case, xy = 24, which is divisible by 6.

Case 2: w=1 and y=3, implying that x=8.
In this case, xy=24, which is divisible by 6.

But if w and y swap values in Case 2, xy will NOT be divisible by 6.
Case 3: w=3 and y=1, implying that x=8.
In this case, xy=8, which is NOT divisible by 6.
INSUFFICIENT.

Cases 1 and 3 also satisfy Statement 2.
Thus, even when both statements are satisfied, it's possible that xy is divisible by 6 or that xy is not divisible by 6.

The correct answer is E.
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