GMAT Question of the Day - Daily to your Mailbox; hard ones only

 It is currently 19 Oct 2019, 02:43 GMAT Club Daily Prep

Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.  M10-19

 new topic post reply Question banks Downloads My Bookmarks Reviews Important topics
Author Message
TAGS:

Hide Tags

Math Expert V
Joined: 02 Sep 2009
Posts: 58452

Show Tags

1
13 00:00

Difficulty:   75% (hard)

Question Stats: 44% (01:21) correct 56% (01:05) wrong based on 82 sessions

HideShow timer Statistics

Is $$X*Y*Z$$ an even integer?

(1) $$X*Y$$ is an even integer.

(2) $$Y*Z$$ is an even integer.

_________________
Math Expert V
Joined: 02 Sep 2009
Posts: 58452

Show Tags

2
Official Solution:

Statements (1) and (2) combined are insufficient. Consider $$X = Y = Z = 2$$ (the answer is "yes") and $$X = Y = Z = \sqrt{2}$$ (the answer is "no"). Do not assume that the numbers are all integers; the stem doesn't stipulate that.

_________________
Manager  Joined: 06 Mar 2014
Posts: 220
Location: India
GMAT Date: 04-30-2015

Show Tags

Bunuel wrote:
Official Solution:

Statements (1) and (2) combined are insufficient. Consider $$X = Y = Z = 2$$ (the answer is "yes") and $$X = Y = Z = \sqrt{2}$$ (the answer is "no"). Do not assume that the numbers are all integers; the stem doesn't stipulate that.

While attempting this question, i tried all possible scenarios (keeping in mind that numbers may not be integers) and ultimately it boiled down to Either C or E.

Somehow could not think of $$\sqrt{2}$$ as a possible option.
I was wondering if we take out the square root scenario, is there any other possible way one could still prove that using Both statements together are insufficient?
Intern  B
Joined: 09 Feb 2015
Posts: 20

Show Tags

Really, it is a good and helpful question, I assumed that all numbers are integer.
Great! I got it.
Senior Manager  Joined: 11 Nov 2014
Posts: 314
Location: India
Concentration: Finance, International Business
WE: Project Management (Telecommunications)

Show Tags

Bunuel Vyshak
when x y z = under-root 2
we are given that x*y & y*z = even
which is under-root 2 * under-root 2 * under-root 2 * under-root 2 = 4
so xyz has to be even
Intern  Joined: 22 Apr 2015
Posts: 11
GMAT 1: 760 Q50 V44 Show Tags

earnit wrote:
While attempting this question, i tried all possible scenarios (keeping in mind that numbers may not be integers) and ultimately it boiled down to Either C or E.

Somehow could not think of $$\sqrt{2}$$ as a possible option.
I was wondering if we take out the square root scenario, is there any other possible way one could still prove that using Both statements together are insufficient?

earnit
If both X and Z are .5 and Y is 4, you will satisfy both statements and still be able to get a "No". That's what I used for solving this problem .
Intern  Joined: 07 Dec 2014
Posts: 3
Location: Australia

Show Tags

Did you not think of 1/3, 6 , 1/3 either?
earnit wrote:
Bunuel wrote:
Official Solution:

Statements (1) and (2) combined are insufficient. Consider $$X = Y = Z = 2$$ (the answer is "yes") and $$X = Y = Z = \sqrt{2}$$ (the answer is "no"). Do not assume that the numbers are all integers; the stem doesn't stipulate that.

While attempting this question, i tried all possible scenarios (keeping in mind that numbers may not be integers) and ultimately it boiled down to Either C or E.

Somehow could not think of $$\sqrt{2}$$ as a possible option.
I was wondering if we take out the square root scenario, is there any other possible way one could still prove that using Both statements together are insufficient?
Intern  Joined: 04 Feb 2016
Posts: 12

Show Tags

1
Just use X=1/2 Y=8 and Z=1/4

I played around with fractions and not square roots. Still got the E for answer
Current Student Joined: 29 Jan 2013
Posts: 40
Location: United States
Schools: Booth PT '20 (M)
GMAT 1: 650 Q50 V26 WE: Manufacturing and Production (Manufacturing)

Show Tags

I think this is a high-quality question and I agree with explanation.
Intern  Joined: 02 Sep 2016
Posts: 12

Show Tags

I think this is a high-quality question and I agree with explanation.
Intern  B
Joined: 06 Feb 2016
Posts: 47
Location: Poland
Concentration: Finance, Accounting
GMAT 1: 730 Q49 V41 GPA: 3.5

Show Tags

My approach was to find a NO answer to this question because it is easy to find a YES answer. X * Y * Z = 1/26 * 52 * 1/4 => NO
Current Student D
Joined: 12 Aug 2015
Posts: 2567
Schools: Boston U '20 (M)
GRE 1: Q169 V154 Show Tags

1
Great Question
Here we need to check if xyz is even or not
Note=> x,y,z are not mentioned to be integers.
Lets go to the statements
Statement 1
xy=even
xy=2
z=2=> xyz=even
z=1/2=> xyz=odd
hence insufficient

Statement 2
yz=even
yz=2
x=2=> xyz=even
x=1/2=> xyz=odd
hence insufficient

Now lets combine the statements
using the test cases
(x,y,z)=>2,2,2=> xyz=even
(x,y,z)=> 1/4,8,1/4=> xyz=8/16=1/2 => neither even nor odd
Hence Insufficient
Hence E
_________________
Senior Manager  G
Joined: 31 May 2017
Posts: 334

Show Tags

stonecold - Hell yeah. Good solution.

I assumed individual X , Y and Z as integer. Careless mistake, but cost me dearly _________________
Please give kudos if it helps

Resources
| | | | |
Intern  B
Joined: 05 Sep 2018
Posts: 1
Concentration: Operations, Strategy

Show Tags

I think this is a high-quality question and I agree with explanation. Yet another easy approach to understand this..
Let say X = 1/3 & Y = 6, X*Y = 2 (Even Int)
Similarly Let say Z = 1/3 & Y = 6, Y*Z = 2 (Even Int)
But X*Y*Z = 1/3*6*1/3 = 2/3 and this is not an even int
Manager  G
Joined: 10 Apr 2018
Posts: 240
Location: India
Concentration: Entrepreneurship, Strategy
GMAT 1: 680 Q48 V34 GPA: 3.3

Show Tags

Bunuel wrote:
Is $$X*Y*Z$$ an even integer?

(1) $$X*Y$$ is an even integer.

(2) $$Y*Z$$ is an even integer.

It's not sufficient to find whether or not one out of X,Y, or Z is an even integer to confirm that X*Y*Z is an even integer since we don't know whether or not all three numbers are integers. We either need to know that all three numbers are integers and that one of them is even or not, or we need exact values of all three numbers.

(1) Let's assume that X*Y=4 and Z=1.2, so X*Y*Z=4.8, which is not an even integer.
However, if X*Y=4, and Z is any integer, X*Y*Z is also an even integer.
So, we don't get a unique nature of X*Y*Z from this statement.
Thus, insufficient.

(2) Similar working as for (1) applies here.
Thus, insufficient.

From (1) and (2) together, we do not get the required information.
Thus, insufficient.

Therefore, the answer is option E. M10-19   [#permalink] 13 Oct 2019, 11:12
Display posts from previous: Sort by

M10-19

 new topic post reply Question banks Downloads My Bookmarks Reviews Important topics

Moderators: chetan2u, Bunuel

 Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne  