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 Your Progress

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.

It appears that you are browsing the GMAT Club forum unregistered!

Signing up is free, quick, and confidential.
Join other 500,000 members and get the full benefits of GMAT Club

Registration gives you:

Tests

Take 11 tests and quizzes from GMAT Club and leading GMAT prep companies such as Manhattan GMAT,
Knewton, and others. All are free for GMAT Club members.

Applicant Stats

View detailed applicant stats such as GPA, GMAT score, work experience, location, application
status, and more

Books/Downloads

Download thousands of study notes,
question collections, GMAT Club’s
Grammar and Math books.
All are free!

Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:

St1:
y(3y+7) = x
3y+7 = x/y
Since 3y + 7 must be integer, then x/y must be integer and x must be a multiple of y if x/y = integer.

St2:
x(x-1) = ym
(x/y)(x-1) = m
Since m is an integer, (x-1) is an integer then x/y must be an integer for the relationship to hold. So x must be a multiple of y.

St1: y(3y+7) = x 3y+7 = x/y Since 3y + 7 must be integer, then x/y must be integer and x must be a multiple of y if x/y = integer.

St2: x(x-1) = ym (x/y)(x-1) = m Since m is an integer, (x-1) is an integer then x/y must be an integer for the relationship to hold. So x must be a multiple of y.

Ans D

I do not think statement 2 can be sufficient. (x-1) and not x may be a multiple of y.

St1: y(3y+7) = x 3y+7 = x/y Since 3y + 7 must be integer, then x/y must be integer and x must be a multiple of y if x/y = integer.

St2: x(x-1) = ym (x/y)(x-1) = m Since m is an integer, (x-1) is an integer then x/y must be an integer for the relationship to hold. So x must be a multiple of y.

Ans D

I do not think statement 2 can be sufficient. (x-1) and not x may be a multiple of y.

If x and y are integers greater than 1, is x a multiple of y?

1) 3y^2 + 7y = x

2) x^2 - x is a multiple of y.

OK lets see...

x/y=N where N is an integer?

1) Y(3Y+7)=x; x/y= (3Y+7) we are told x and y are integers...therefor RHS is an integer...which inturn means RHS is an integer...therefore X is a multiple..sufficient..

2) x(x-1)=y/N ...we dont know if X or X-1 is the multiple of Y..therefore insufficient...

If x and y are integers greater than 1, is x a multiple of y?

1) 3y^2 + 7y = x 2) x^2 - x is a multiple of y

A too...........

from 1: 3y^2 + 7y = x
y (3y + 7) = x
in this case, 3y+7 is an integer. so x is a multiple of x.

from 2: x^2 - x = yk
x (x -1) = yk
x (x -1) = yk
k could be or could not be x or x-1. suppose, x = 4, x-1=3, k =1 and y = 12. in this case x is not a multiple of y. if x = 4, x-1 = 3, y = 3 and k =4, x is a multiple of y.

gmatclubot

Re: DS - number properties
[#permalink]
25 Jul 2007, 09:57