GMAT Question of the Day - Daily to your Mailbox; hard ones only

It is currently 16 Jan 2019, 04:21

Close

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
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.

Close

Request Expert Reply

Confirm Cancel
Events & Promotions in January
PrevNext
SuMoTuWeThFrSa
303112345
6789101112
13141516171819
20212223242526
272829303112
Open Detailed Calendar
  • The winning strategy for a high GRE score

     January 17, 2019

     January 17, 2019

     08:00 AM PST

     09:00 AM PST

    Learn the winning strategy for a high GRE score — what do people who reach a high score do differently? We're going to share insights, tips and strategies from data we've collected from over 50,000 students who used examPAL.
  • Free GMAT Strategy Webinar

     January 19, 2019

     January 19, 2019

     07:00 AM PST

     09:00 AM PST

    Aiming to score 760+? Attend this FREE session to learn how to Define your GMAT Strategy, Create your Study Plan and Master the Core Skills to excel on the GMAT.

xy and yx are a pair of reversed two digit positive integers. If x^2-y

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

Hide Tags

 
VP
VP
avatar
P
Joined: 07 Dec 2014
Posts: 1150
xy and yx are a pair of reversed two digit positive integers. If x^2-y  [#permalink]

Show Tags

New post 26 Aug 2018, 14:03
4
00:00
A
B
C
D
E

Difficulty:

  85% (hard)

Question Stats:

43% (02:27) correct 57% (02:13) wrong based on 44 sessions

HideShow timer Statistics

xy and yx are a pair of reversed two digit positive integers. If x^2-y^2=45, how many such pairs are there?

A. 0
B. 1
C. 2
D. 3
E. 4
Senior SC Moderator
avatar
V
Joined: 22 May 2016
Posts: 2329
xy and yx are a pair of reversed two digit positive integers. If x^2-y  [#permalink]

Show Tags

New post 26 Aug 2018, 17:44
gracie wrote:
xy and yx are a pair of reversed two digit positive integers. If x^2-y^2=45, how many such pairs are there?

A. 0
B. 1
C. 2
D. 3
E. 4

If \(x^2-y^2=45\), then
\((x+y)(x-y)=45\)

\((x+y)=a\): one factor of 45
\((x-y)=b\): another factor of 45

Factors of 45
\((a)*(b)=45\)
\(1*45=45\)
\(3*15=45\)
\(5*9=45\)

The first set of factors will not work
\(x+y=45\)
\(x-y=1\) Add
\(2x=46\)
\(x=23\)

Second set of factors
\(x+y=15\)
\(x-y=3\) Add
\(2x=18\)
\(x=9\)

\(x-y=3\)
\(9-y=3\)
\(y=6\)

One pair, xy and yx: 96 and 69
\((x^2-y^2)=(9^2-6^2)=(81-36)=45\)

Third set of factors
\(x+y=9\)
\(x-y=5\) Add
\(2x=14\)
\(x=7\)

\(x-y=5\)
\(7-y=5\)
\(y=2\)

Another pair: 72 and 27
\((x^2-y^2)=(7^2-2^2)=(49-4)=45\)

There are no more factor sets.

xy and yx are
96 and 69
72 and 27

Number of pairs: 2

Answer C
_________________

Never look down on anybody unless you're helping them up.
--Jesse Jackson

GMAT Club Bot
xy and yx are a pair of reversed two digit positive integers. If x^2-y &nbs [#permalink] 26 Aug 2018, 17:44
Display posts from previous: Sort by

xy and yx are a pair of reversed two digit positive integers. If x^2-y

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


Copyright

GMAT Club MBA Forum Home| About| Terms and Conditions and Privacy Policy| GMAT Club Rules| Contact| Sitemap

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®.