If x and y are integers greater than 1, is x a multiple of y?
a. 3y2 + 7y = x
b. x2 - x is a multiple of y
Answer is A. Could someone help me to solve this?
Cheers!
5-Day Free Trial
5-day free, full-access trial TTP
Available with Beat the GMAT members only code
MORE DETAILS
Is x a multiple of y?
This topic has expert replies
-
Frankenstein
- Legendary Member
- Posts: 1448
- Joined: Tue May 17, 2011 9:55 am
- Location: India
- Thanked: 375 times
- Followed by:53 members
hi,
From(1): 3y^2+7y = x
So, x = y(3y+7) = y*(integer)
So, x is multiple of y
Sufficient
From(2): x(x-1) = ky
Not sufficient
Hence, A
From(1): 3y^2+7y = x
So, x = y(3y+7) = y*(integer)
So, x is multiple of y
Sufficient
From(2): x(x-1) = ky
Not sufficient
Hence, A
Cheers!
Things are not what they appear to be... nor are they otherwise
Things are not what they appear to be... nor are they otherwise
GMAT/MBA Expert
-
Anurag@Gurome
- GMAT Instructor
- Posts: 3835
- Joined: Fri Apr 02, 2010 10:00 pm
- Location: Milpitas, CA
- Thanked: 1854 times
- Followed by:523 members
- GMAT Score:770
Statement 1: x = y(3y + 7) = y*(Some integer)Ahmed MS wrote:If x and y are integers greater than 1, is x a multiple of y?
a. 3y² + 7y = x
b. x² - x is a multiple of y
Therefore, x is a multiple of y
Sufficient
Statement 2: x(x - 1) is a multiple of y.
Therefore, either x or (x - 1) or none of them is multiple of y.
Not sufficient
The correct answer is A.
Last edited by Anurag@Gurome on Fri Jun 17, 2011 1:13 am, edited 2 times in total.
Anurag Mairal, Ph.D., MBA
GMAT Expert, Admissions and Career Guidance
Gurome, Inc.
1-800-566-4043 (USA)
Join Our Facebook Groups
GMAT with Gurome
https://www.facebook.com/groups/272466352793633/
Admissions with Gurome
https://www.facebook.com/groups/461459690536574/
Career Advising with Gurome
https://www.facebook.com/groups/360435787349781/
GMAT Expert, Admissions and Career Guidance
Gurome, Inc.
1-800-566-4043 (USA)
Join Our Facebook Groups
GMAT with Gurome
https://www.facebook.com/groups/272466352793633/
Admissions with Gurome
https://www.facebook.com/groups/461459690536574/
Career Advising with Gurome
https://www.facebook.com/groups/360435787349781/
-
kevincanspain
- GMAT Instructor
- Posts: 613
- Joined: Thu Mar 22, 2007 6:17 am
- Location: madrid
- Thanked: 171 times
- Followed by:64 members
- GMAT Score:790
It is important to note that x and x-1 share no prime factors. In other words, the only factor they have in common is 1. Thus either x or x-1 is a multiple of y, but it is impossible for both of them to be a multiple of y!
Kevin Armstrong
GMAT Instructor
Gmatclasses
Madrid
GMAT Instructor
Gmatclasses
Madrid
-
Frankenstein
- Legendary Member
- Posts: 1448
- Joined: Tue May 17, 2011 9:55 am
- Location: India
- Thanked: 375 times
- Followed by:53 members
Hi,kevincanspain wrote:It is important to note that x and x-1 share no prime factors. In other words, the only factor they have in common is 1. Thus either x or x-1 is a multiple of y, but it is impossible for both of them to be a multiple of y!
Not necessarily.
If x= 10 and y=6
x(x-1) = 90 is multiple of 6 but neither x nor (x-1) is multiple of y.
Cheers!
Things are not what they appear to be... nor are they otherwise
Things are not what they appear to be... nor are they otherwise
-
kevincanspain
- GMAT Instructor
- Posts: 613
- Joined: Thu Mar 22, 2007 6:17 am
- Location: madrid
- Thanked: 171 times
- Followed by:64 members
- GMAT Score:790
Right! Either x or x-1 or neither of these two expressions is a multiple of y
Kevin Armstrong
GMAT Instructor
Gmatclasses
Madrid
GMAT Instructor
Gmatclasses
Madrid
-
amit2k9
- Master | Next Rank: 500 Posts
- Posts: 461
- Joined: Tue May 10, 2011 9:09 am
- Location: pune
- Thanked: 36 times
- Followed by:3 members
a y(3y+7) = x 3y+7 = constant meaning y*k = x sufficient.
b x(x-1)/y = integer (as it is multiple)
(x/y)* (x-1) can be analysed as x=y=2 or x=3,y=2. not sufficient.
thus A it clean.
b x(x-1)/y = integer (as it is multiple)
(x/y)* (x-1) can be analysed as x=y=2 or x=3,y=2. not sufficient.
thus A it clean.
For Understanding Sustainability,Green Businesses and Social Entrepreneurship visit -https://aamthoughts.blocked/
(Featured Best Green Site Worldwide-https://bloggers.com/green/popular/page2)
(Featured Best Green Site Worldwide-https://bloggers.com/green/popular/page2)
-
[email protected]
- Master | Next Rank: 500 Posts
- Posts: 218
- Joined: Wed Dec 11, 2013 4:02 am
- Thanked: 3 times
- Followed by:4 members
What's the logic behind none of them is a multiple of y?Anurag@Gurome wrote:Statement 1: x = y(3y + 7) = y*(Some integer)Ahmed MS wrote:If x and y are integers greater than 1, is x a multiple of y?
a. 3y² + 7y = x
b. x² - x is a multiple of y
Therefore, x is a multiple of y
Sufficient
Statement 2: x(x - 1) is a multiple of y.
Therefore, either x or (x - 1) or none of them is multiple of y.
Not sufficient
The correct answer is A.
-
GMATGuruNY
- 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
If y is equal to the product of a factor of x and a factor of x-1, then (x)(x-1) will be a multiple of y, but neither x nor x-1 on its own will be a multiple of y.[email protected] wrote:What's the logic behind none of them is a multiple of y?Anurag@Gurome wrote:Statement 1: x = y(3y + 7) = y*(Some integer)Ahmed MS wrote:If x and y are integers greater than 1, is x a multiple of y?
a. 3y² + 7y = x
b. x² - x is a multiple of y
Therefore, x is a multiple of y
Sufficient
Statement 2: x(x - 1) is a multiple of y.
Therefore, either x or (x - 1) or none of them is multiple of y.
Not sufficient
The correct answer is A.
To illustrate:
Let x=9, implying that x-1 = 8 and that (x)(x-1) = 9*8 = 72.
If y is equal to the product of 3 (a factor of x) and 2 (a factor of x-1), then y = 3*2 = 6.
In this case:
(x)(x-1) = 72 is a multiple of y=6, but neither x=9 nor x-1=8 on its own is a multiple of y=6.
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
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
GMAT/MBA Expert
-
[email protected]
- Elite Legendary Member
- Posts: 10392
- Joined: Sun Jun 23, 2013 6:38 pm
- Location: Palo Alto, CA
- Thanked: 2867 times
- Followed by:511 members
- GMAT Score:800
Hi All,
This DS question can be solved by TESTing VALUES.
We're told that X and Y are INTEGERS that are both > 1. We're asked if X is a multiple of Y. This is a YES/NO question.
Fact 1: 3(Y^2) + 7Y = X
IF....
Y = 2, then X = 26 and the answer to the question is YES.
Y = 3, then X = 48 and the answer to the question is YES.
Y = 4, then X = 76 and the answer to the question is YES.
Y = 5, then X = 110 and the answer to the question is YES.
Etc.
The answer is ALWAYS YES
Fact 1 is SUFFICIENT
Fact 2: X^2 - X is a multiple of Y
IF...
X = 2, then Y would have to be = 2 and the answer to the question is YES
X = 3, then Y could be = 2, 3 OR 6. IF Y = 2, then the answer to the question is NO
Fact 2 is INSUFFICIENT
Final Answer: A
GMAT assassins aren't born, they're made,
Rich
This DS question can be solved by TESTing VALUES.
We're told that X and Y are INTEGERS that are both > 1. We're asked if X is a multiple of Y. This is a YES/NO question.
Fact 1: 3(Y^2) + 7Y = X
IF....
Y = 2, then X = 26 and the answer to the question is YES.
Y = 3, then X = 48 and the answer to the question is YES.
Y = 4, then X = 76 and the answer to the question is YES.
Y = 5, then X = 110 and the answer to the question is YES.
Etc.
The answer is ALWAYS YES
Fact 1 is SUFFICIENT
Fact 2: X^2 - X is a multiple of Y
IF...
X = 2, then Y would have to be = 2 and the answer to the question is YES
X = 3, then Y could be = 2, 3 OR 6. IF Y = 2, then the answer to the question is NO
Fact 2 is INSUFFICIENT
Final Answer: A
GMAT assassins aren't born, they're made,
Rich
