Doubt With OA

Expert replies

Previous Topic Next Topic

Fatehdeep Singh: Junior | Next Rank: 30 Posts; Posts: 10; Joined: Fri Feb 19, 2010 7:05 am; Thanked: 2 times

by Fatehdeep Singh » Sun May 29, 2011 8:15 pm

x > y^2 ?

I) x>y+5
II)x^2 - y^2 =0

OA after some discussions?

Deg Teg Fateh!!!

Like this post

Source: Beat The GMAT — Data Sufficiency | Sun May 29, 2011 8:15 pm

cans: Legendary Member; Posts: 1309; Joined: Mon Apr 04, 2011 5:34 amFollowed by: 123 members; Location: India; Thanked: 310 times; GMAT Score:750

by cans » Sun May 29, 2011 8:36 pm

IMO C

Like this post

sivaelectric: Master | Next Rank: 500 Posts; Posts: 439; Joined: Sat Aug 09, 2008 8:32 amFollowed by: 28 members; Location: India; Thanked: 34 times

by sivaelectric » Sun May 29, 2011 9:10 pm

IMO A

If I am wrong correct me

, If my post helped let me know by clicking the Thanks button

.

Chitra Sivasankar Arunagiri

Like this post

cans: Legendary Member; Posts: 1309; Joined: Mon Apr 04, 2011 5:34 amFollowed by: 123 members; Location: India; Thanked: 310 times; GMAT Score:750

by cans » Sun May 29, 2011 9:33 pm

x>y^2?

I) x>y+5 - suppose y=1, x>6 and x>1^2
if y=9, x>14 we can't say that x>81.
Thus A insufficient.

II)x^2 - y^2 =0
=> either x=y or x=-y
now if x=y, and x=y=1, x>y^2 not true
x=y=0.5, x>y^2 true,
Thus B alone not sufficient.

A&B together,
x>y+5 => x not equal to y, thus x=-y
x>-x+5 => x>5/2
Now to find if x>y^2 or to find if x>(-x)^2 or to find if x > x^2
As x>2.5, thus x < x^2
Thus not true. Sufficient
Hence C.

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 » Sun May 29, 2011 9:44 pm

Fatehdeep Singh wrote:x > y^2 ?

I) x>y+5
II)x^2 - y^2 =0

OA after some discussions?

Solution:
Consider first I alone.
Let x = 5 and y = -1.
Here (x = 5) > (y+5 = -1+5 = 4) and (x = 5) > (y^2 = 1).
Next let x = -1/3 and y = -6.
Now, -1/3 = x > -6+5 = -1.
But x = -1/3 < y^2 = 36.
So, nothing definite can be said from (1) alone.
Next consider II) alone.
Let x = -1 and y = 1.
So, x = -1 < y^2 = 1.
Next, let x = 1/2 and y = 1/2.
So, x = Â½ > y^2 = Â¼.
Again, nothing definite can be said from (2) alone.
Lastly, combine both statements and check.
If x > y+5, we get that x > y.
Or x is not equal to y.
Now II means that (x+y)(x-y) = 0.
This means that x = -y.
Now, x > y+5 means that -y > y+5 or y < -5/2.
Now x > y^2 means that -y > y^2 or y^2+y < 0 or -1<y<0.
This is not possible because y <-5/2.
So, the answer to the main question is "no".
Or, both statements together are sufficient to answer the question.

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

sivaelectric: Master | Next Rank: 500 Posts; Posts: 439; Joined: Sat Aug 09, 2008 8:32 amFollowed by: 28 members; Location: India; Thanked: 34 times

by sivaelectric » Sun May 29, 2011 9:54 pm

Fatehdeep Singh wrote:x > y^2 ?

I) x>y+5
II)x^2 - y^2 =0

OA after some discussions?

Can someone please explain why this procedure is wrong?

X>Y+5
X-Y>5, we can take X=7 and Y=1 so that X-Y more than 5. now X = 7 > Y^2 = 1

@Anurag Sir, can you please correct me?

If I am wrong correct me

, If my post helped let me know by clicking the Thanks button

.

Chitra Sivasankar Arunagiri

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 » Sun May 29, 2011 10:00 pm

sivaelectric wrote:
Fatehdeep Singh wrote:x > y^2 ?

I) x>y+5
II)x^2 - y^2 =0

OA after some discussions?
Can someone please explain why this procedure is wrong?

X>Y+5
X-Y>5, we can take X=7 and Y=1 so that X-Y more than 5. now X = 7 > Y^2 = 1

@Anurag Sir, can you please correct me?

If you are just considering statement I, this example is fine but if you are combining and checking, then x^2 = 49 is not equal to y^2 = 1. So condition in II is not being satisfied.
This example will not hold then.

Like this post

sivaelectric: Master | Next Rank: 500 Posts; Posts: 439; Joined: Sat Aug 09, 2008 8:32 amFollowed by: 28 members; Location: India; Thanked: 34 times

by sivaelectric » Sun May 29, 2011 10:03 pm

Sir, But when you get an answer with the first one itself, should you have to go for the second one. But as I type this I am also starting to get another doubt about this.

When the first hint gives you an answer, should you check the same values with the second one too? Is it like that?

If I am wrong correct me

, If my post helped let me know by clicking the Thanks button

.

Chitra Sivasankar Arunagiri

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 » Sun May 29, 2011 10:26 pm

sivaelectric wrote:Sir, But when you get an answer with the first one itself, should you have to go for the second one. But as I type this I am also starting to get another doubt about this.

When the first hint gives you an answer, should you check the same values with the second one too? Is it like that?

You are not going to get the answer with just this example.
Take x =-1/3 and y = -6.
Here also x=-1/3 > y+5 = -1 but x = -1/3 < y^2 = 36.
This means I being true does not mean that x > y^2.
Or I alone is not sufficient.
Now, check II alone.
Take values that satisfy only II and have nothing to do with I.
Again you will not get a definite answer.
This means that II alone is not sufficient.
Next check with values that satisfy both I ans II simultaneously.
Then try to get the answer to the main question.

Like this post

sivaelectric: Master | Next Rank: 500 Posts; Posts: 439; Joined: Sat Aug 09, 2008 8:32 amFollowed by: 28 members; Location: India; Thanked: 34 times

by sivaelectric » Sun May 29, 2011 11:32 pm

Great explanation Anurag Sir

If I am wrong correct me

, If my post helped let me know by clicking the Thanks button

.

Chitra Sivasankar Arunagiri

Like this post

Post new topic Post Reply

• Page 1 of 1

GMAT Course Reviews

560 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