BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

MGMAT Advanced quant - Hybrid problem

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
User avatar
Legendary Member
Posts: 979
Joined: Tue Apr 14, 2009 1:38 am
Location: Hyderabad, India
Thanked: 49 times
Followed by:12 members
GMAT Score:700

MGMAT Advanced quant - Hybrid problem

by bubbliiiiiiii » Mon Aug 31, 2015 10:37 pm
If x and y are positive integers greater than 1 such that x − y and are both even integers, which of the following numbers must be non-prime integers?

I. x
II. x + y
III. y/x

(A) I only (B) II only (C) III only (D) I and II only (E) I, II and III

Manhattan Prep (2015-05-17). GMAT Advanced Quant (Kindle Locations 4076-4082). Manhattan Prep Publishing. Kindle Edition.

OA D. Why not E?

IMO, III always results in a positive fraction and thus is not prime always. Please let me know what am I missing.
Regards,

Pranay
Top
Source: — Problem Solving |
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 » Tue Sep 01, 2015 3:10 am
If x and y are positive integers greater than 1 such that x - y and x/y are both even integers, which of the following numbers must be non-prime integers?

I. x
II. x + y
III. y/x

(A) I only (B) II only (C) III only (D) I and II only (E) I, II and III
The problem should read as shown above.
bubbliiiiiiii wrote: IMO, III always results in a positive fraction and thus is not prime always. Please let me know what am I missing.
III: y/x
If x=4 and y=2, then y/x = 2/4 = 1/2.
Since 1/2 is not a non-prime INTEGER, III does not have to be true.
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
Top
User avatar
Elite Legendary Member
Posts: 3991
Joined: Fri Jul 24, 2015 2:28 am
Location: Las Vegas, USA
Thanked: 19 times
Followed by:37 members

by Max@Math Revolution » Wed Sep 02, 2015 9:31 pm
Forget conventional ways of solving math questions. In PS, IVY approach is the easiest and quickest way to find the answer.


If x and y are positive integers greater than 1 such that x - y and x/y are both even integers, which of the following numbers must be non-prime integers?

I. x
II. x + y
III. y/x

(A) I only (B) II only (C) III only (D) I and II only (E) I, II and III
==> x/y=even, x=y*even=even, x-y=even,even-y=even, y=even-even=even therefore x=y=even. Since x/y=x/even=even, x=even*even=a multiple of 4. Therefore, x=4n, y=2m(n,m are integers).

I. x ==> x=4n=multiple of 4, therefore is not a prime number
II. x + y ==> x+y=4n+2m=2(2n+m)=even, therefore it is not a prime number.
III. y/x ==> y/x=2m/4n=m/2n is NOT integer therefore it is not a prime number (since we need non-prime integers)

Therefore the answer is D.


www.mathrevolution.com
l The one-and-only World's First Variable Approach for DS and IVY Approach for PS that allow anyone to easily solve GMAT math questions.

l The easy-to-use solutions. Math skills are totally irrelevant. Forget conventional ways of solving math questions.

l The most effective time management for GMAT math to date allowing you to solve 37 questions with 10 minutes to spare

l Hitting a score of 45 is very easy and points and 49-51 is also doable.

l Unlimited Access to over 120 free video lessons at https://www.mathrevolution.com/gmat/lesson

Our advertising video at https://www.youtube.com/watch?v=R_Fki3_2vO8
Top
Post new topic Post Reply
• Page 1 of 1