It is currently 17 Mar 2018, 17:28

### GMAT Club Daily Prep

#### 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

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

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# If x² - y² = 55, and x - y = 11, then y =

 new topic post reply Question banks Downloads My Bookmarks Reviews Important topics
Author Message
TAGS:

### Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 44290
If x² - y² = 55, and x - y = 11, then y = [#permalink]

### Show Tags

12 May 2016, 01:58
Expert's post
2
This post was
BOOKMARKED
00:00

Difficulty:

15% (low)

Question Stats:

77% (01:12) correct 23% (01:06) wrong based on 136 sessions

### HideShow timer Statistics

If x^2 - y^2 = 55, and x - y = 11, then y =

A. 8
B. 5
C. 3
D. -8
E. -3
[Reveal] Spoiler: OA

_________________
Intern
Joined: 07 May 2016
Posts: 26
If x² - y² = 55, and x - y = 11, then y = [#permalink]

### Show Tags

12 May 2016, 07:10
1
KUDOS
1
This post was
BOOKMARKED
Bunuel wrote:
If x^2 - y^2 = 55, and x - y = 11, then y =

A. 8
B. 5
C. 3
D. -8
E. -3

Hi
we have x - y = 11
=> x = 11+y
replace x into the first equation
=>$$(11+y)^2 - y^2 = 55$$
EXPANDING:
=>$$(11)^2 + 2*(11)*y + y^2 - y^2 = 55$$
=>$$121 + 22y = 55$$
=>$$22y = 55 - 121$$
=>$$22y = -66$$
=>$$y = -66/22 = -3$$
=> answer is E (-3)

Last edited by HungNguyen on 12 May 2016, 08:18, edited 1 time in total.
Board of Directors
Status: QA & VA Forum Moderator
Joined: 11 Jun 2011
Posts: 3349
Location: India
GPA: 3.5
WE: Business Development (Commercial Banking)
Re: If x² - y² = 55, and x - y = 11, then y = [#permalink]

### Show Tags

12 May 2016, 07:56
Bunuel wrote:
If x^2 - y^2 = 55, and x - y = 11, then y =

A. 8
B. 5
C. 3
D. -8
E. -3

$$x^2 - y^2$$ = $$( x - y )( x + y )$$

$$55$$ = $$( 11 )( x + y )$$

$$5$$ = $$x + y$$-------> (1)

$$11$$ = $$x - y$$-------> (2)

$$2x$$ = $$16$$

Or, $$x$$ = $$8$$

SO,$$y$$ = $$-3$$

Hence answer will be (E)

_________________

Thanks and Regards

Abhishek....

PLEASE FOLLOW THE RULES FOR POSTING IN QA AND VA FORUM AND USE SEARCH FUNCTION BEFORE POSTING NEW QUESTIONS

How to use Search Function in GMAT Club | Rules for Posting in QA forum | Writing Mathematical Formulas |Rules for Posting in VA forum | Request Expert's Reply ( VA Forum Only )

Current Student
Joined: 18 Oct 2014
Posts: 901
Location: United States
GMAT 1: 660 Q49 V31
GPA: 3.98
Re: If x² - y² = 55, and x - y = 11, then y = [#permalink]

### Show Tags

12 May 2016, 11:29
(x+y)(x-y)= 55

x+y= 5 (its given that (x-y)= 11)

Solving two equations:-

x+y=5
x-y=11

y= -3
_________________

I welcome critical analysis of my post!! That will help me reach 700+

Non-Human User
Joined: 09 Sep 2013
Posts: 6531
Re: If x² - y² = 55, and x - y = 11, then y = [#permalink]

### Show Tags

15 Oct 2017, 09:49
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________
Re: If x² - y² = 55, and x - y = 11, then y =   [#permalink] 15 Oct 2017, 09:49
Display posts from previous: Sort by

# If x² - y² = 55, and x - y = 11, then y =

 new topic post reply Question banks Downloads My Bookmarks Reviews Important topics

 Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.