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:

Re: If x and y are two different prime numbers, which of the [#permalink]

Show Tags

08 Jun 2012, 09:29

Expert's post

sarb wrote:

If x and y are two different prime numbers, which of the following cannot be true?

A. xy is odd. B. x + y is even. C. x + y is odd. D. xy is even. E. x/y is an integer

A prime number is a positive integer with exactly two distinct positive divisors: 1 and itself. So, a prime number cannot be a multiple of another prime number. Which makes option E not possible (x/y=integer means that x is a multiple of y).

Answer: E.

All other options are possible: A. xy is odd --> x=3 and y=5; B. x + y is even --> x=3 and y=5; C. x + y is odd --> x=2 and y=3; D. xy is even --> x=2 and y=3;

Re: If x and y are two distinct prime numbers, which of the following cann [#permalink]

Show Tags

09 Sep 2014, 19:28

Hi PareshGmat,

The best way to attack this question is to Plug-In simple prime numbers to prove the answer choices. Don't forget that 2 is the first prime number, and also the only even one. As a refresher, the definition of a prime number is a natural number greater than 1 that has no positive divisors other than 1 and itself.

(A) x*y is odd. Let's choose x=3, y=5, so x*y = 15.

(B) x*y is even. Let's choose x=2, y=3, so x*y = 10.

(C) x-y is odd. Let's choose x=3, y=2, so x-y = 1.

(D) x-y is even. Let's choose x=5, y=3, so x-y = 2.

Thus, E is the only answer choice left, and must be the answer.

Re: If x and y are two distinct prime numbers, which of the following cann [#permalink]

Show Tags

09 Sep 2014, 21:05

Expert's post

PareshGmat wrote:

If x and y are two distinct prime numbers, which of the following cannot be true?

A. xy is odd. B. xy is even. C. x - y is odd. D. x - y is even. E. \(\frac{x^2}{y}\) is an integer

Whenever you come across prime numbers and the terms odd and even in a question, you must think of 2 - the only even prime number. All other prime numbers are odd.

A. xy is odd. If both x and y are odd, xy can be odd.

B. xy is even. If one of x and y is 2 and the other is some other odd prime number, xy will be even.

C. x - y is odd. If x is odd and y is 2, x-y will be odd.

D. x - y is even. If both x and y are odd, x-y will be even.

So all these are possible. Then answer must be (E). Logically, if x is prime and y is a different prime number, x^2 cannot be divisible by y. _________________

So, my final tally is in. I applied to three b schools in total this season: INSEAD – admitted MIT Sloan – admitted Wharton – waitlisted and dinged No...

A few weeks ago, the following tweet popped up in my timeline. thanks @Uber_Mumbai for showing me what #daylightrobbery means!I know I have a choice not to use it...

“This elective will be most relevant to learn innovative methodologies in digital marketing in a place which is the origin for major marketing companies.” This was the crux...