Positive ?

Expert replies

Previous Topic Next Topic

karthikpandian19: Legendary Member; Posts: 1665; Joined: Thu Nov 03, 2011 7:04 pmFollowed by: 70 members; Thanked: 165 times

by karthikpandian19 » Fri Jan 06, 2012 2:57 pm

Are x and y positive?

1. 2x-2y=1
2.x/y >1

Like this post

Source: Beat The GMAT — Problem Solving | Fri Jan 06, 2012 2:57 pm

pemdas: Legendary Member; Posts: 1084; Joined: Fri Apr 15, 2011 2:33 pmFollowed by: 21 members; Thanked: 158 times

by pemdas » Fri Jan 06, 2012 3:24 pm

st(1) (x-y)=1/2 :: x and y can have any sign, Not Sufficient
st(2) implies either both are -ve or +ve along with |x|>|y|, Not Sufficient
combined st(1&2): If |x|>|y| we may have only two +ve signs for x and y according to st(2). With -ve signs of x,y it's impossible to have (x-y)=1/2 as |x|>|y|
hence x,y have +ve signs and |x|>|y|. Answer Yes, Sufficient.

c

karthikpandian19 wrote:Are x and y positive?

1. 2x-2y=1
2.x/y >1

Success doesn't come overnight!

Like this post

karthikpandian19: Legendary Member; Posts: 1665; Joined: Thu Nov 03, 2011 7:04 pmFollowed by: 70 members; Thanked: 165 times

by karthikpandian19 » Fri Jan 06, 2012 3:35 pm

Can you explain why have you added MODULUS in your second statement and then also when combining them.

pemdas wrote:st(1) (x-y)=1/2 :: x and y can have any sign, Not Sufficient
st(2) implies either both are -ve or +ve along with |x|>|y|, Not Sufficient
combined st(1&2): If |x|>|y| we may have only two +ve signs for x and y according to st(2). With -ve signs of x,y it's impossible to have (x-y)=1/2 as |x|>|y|
hence x,y have +ve signs and |x|>|y|. Answer Yes, Sufficient.

c
karthikpandian19 wrote:Are x and y positive?

1. 2x-2y=1
2.x/y >1

Like this post

pemdas: Legendary Member; Posts: 1084; Joined: Fri Apr 15, 2011 2:33 pmFollowed by: 21 members; Thanked: 158 times

the

by pemdas » Fri Jan 06, 2012 4:17 pm

st(2) x/y >1

The numerator should be greater than the denominator and signs must be the same - both +ve or both -ve

For mathematical convenience I added modulus, as |x|>|y|.

Success doesn't come overnight!

Like this post

GMAT/MBA Expert

Anurag@Gurome: GMAT Instructor; Posts: 3835; Joined: Fri Apr 02, 2010 10:00 pmFollowed by: 523 members; Location: Milpitas, CA; Thanked: 1854 times; GMAT Score:770

by Anurag@Gurome » Fri Jan 06, 2012 9:44 pm

karthikpandian19 wrote:Are x and y positive?

1. 2x-2y=1
2.x/y >1

(1) 2x - 2y = 1
Implies (x - y) = 1/2. This means the only case that is not possible is x negative and y positive. In that case the LHS will be negative always! So the possible cases are (with examples),
(1) x positive, y positive (x = 4.5, y = 4)
(2) x positive, y negative (x = 0.25, y = -0.25)
(3) x = 0.5, y = 0
(4) x = 0 , y = -0.5
(5) x negative, y negative (x = -4, y = -4.5)

(Note : In each case there is also some constraints. Like in the 1st case, not for all positive x, y the relation will hold! x must be equal to (y + 0.5) etc.) ; NOT sufficient.

(2) (x/y) > 1
Again this implies any one of the following two cases,
(1) Both of them are positive and x > y
(2) Both of them are negative and x < y; NOT sufficient.

Combining (1) and (2) together, (2) limits the number of possible cases to two. So, let's analyze them again with the help of statement 1.
(1) Both of them are positive and x > y => (x - y) = 0.5 is possible.
(2) Both of them are negative and x < y => (x - y) will be always negative. Not possible.

Thus, x and y are both positive; SUFFICIENT.

The correct answer is C.

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/

Like this post

GMATGuruNY: GMAT Instructor; Posts: 15539; Joined: Tue May 25, 2010 12:04 pmFollowed by: 1906 members; Location: New York, NY; Thanked: 13060 times; GMAT Score:790

by GMATGuruNY » Sat Jan 07, 2012 5:54 am

I posted a solution here:

https://www.beatthegmat.com/are-x-and-y- ... 89906.html

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

Like this post

sam2304: Legendary Member; Posts: 1239; Joined: Tue Apr 26, 2011 6:25 amFollowed by: 26 members; Thanked: 233 times; GMAT Score:680

by sam2304 » Sat Jan 07, 2012 9:05 am

IMO C.

Are x and y +ve ?

1.x-y = 1/2. Nothing about the signs of both X and Y. INSUFF
2.x > y if both are +ve and x < y if both are -ve. INSUFF

Combining both 1 and 2.
If both are positive then x-y=1/2 is possible and hence Yes to the question.
If both are negative then x-y=1/2 cannot be arrived at. So both must be +ve.
Together SUFF.

Getting defeated is just a temporary notion, giving it up is what makes it permanent.
https://gmatandbeyond.blogspot.in/

Like this post

MakeUrTimeCount: Master | Next Rank: 500 Posts; Posts: 104; Joined: Sun Dec 11, 2011 1:25 pmFollowed by: 3 members; Thanked: 11 times

by MakeUrTimeCount » Mon Jan 09, 2012 12:30 am

I know everyone in the thread is supporting C. But I think it is E.

1. 2x-2y=1
=>x = y + .5
Not-sufficient either can be positive or negative.

2.x/y >1
Both should be positive or negetive.

Using both 1) and 2):
x = y + .5 and x> y

If x = -1/2 , y = -1,
x = y + .5 => True
x > y => True

If x = 1 , y = 1/2,
x = y + .5 => True
x> y => True

Answer E.

Like this post

ronnie1985: Legendary Member; Posts: 626; Joined: Fri Dec 23, 2011 2:50 amFollowed by: 10 members; Location: Ahmedabad; Thanked: 31 times

by ronnie1985 » Mon Jan 09, 2012 1:56 am

Both the statements are not sufficient together.
First statement gives: x-y = 1/2, does not give anything about sign of x or y
Second statement just says that x>y, does not say anything about signs of x and y
Together the statements give same information that x>y by 1/2.

Follow your passion, Success as perceived by others shall follow you

Like this post

Post new topic Post Reply

• Page 1 of 1

GMAT Course Reviews

559 reviews

1168 reviews

431 reviews

359 reviews

147 reviews

5/5

5 Star (560 Reviews)

"Target Test Prep is the closest to the official version of the GMAT exam, about 99% accuracy in terms of the quality and quantity of information. The course has excellently created singular sets of focused lessons and tests for every possible topic that one could come across in the official GMAT exam."

"The TTP course maximizes the efficiency of the time you spend studying. It will take time and effort but I could almost guarantee that if you complete the course exactly as it is laid out you will get an amazing score. They also have a very responsive team willing to help with any questions you might have."

"TTP has two things that I think no other test prep company offers: A teaching approach that reinforces understanding and an attitude that will give you the mental preparedness needed to succeed on the test. TTP gives you a deep understanding of the concept you need to know while teaching you how to think."

Write a Review