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

Redeem
TTP OnDemand GMAT Video Course
Featured Course

Target Test Prep GMAT OnDemand

Scott Woodbury-Stewart’s private virtual classroom — 400 hours of master-class video lessons for the GMAT Focus Edition.

  • 715+ score guarantee — highest in the industry (99th percentile)
  • 52 chapters · 1,500+ lessons · 4,000+ practice questions
  • 400 hours of video · 1,500+ instructor-led HD smartboard lessons
  • 300,000+ students accepted to Harvard, Stanford, Wharton, Booth & Sloan & more
  • 24/7 live support + weekly Zoom office hours with GMAT instructors
  • TTP AI Assist — 24/7 AI-powered virtual tutor for instant help
  • 1,200+ flashcards + AI-powered study assistant & daily calendar
  • OnDemand, LiveTeach & GMAT Bootcamp formats available
  • Also: GRE, SAT Math & Executive Assessment courses
  • MBA Admissions Consulting now available
  • 🏆 2025 EdTech Breakthrough Award: Test Prep Solution Provider of the Year
  • 200,000+ students served
  • 5-day free trial — $0 to start, no auto-billing, cancel anytime
★★★★★ 5.0 (559 reviews)
130-pt guarantee
$0 to start then $127/mo
Start Free 5-Day Trial Read 559 Reviews →

Does x = y ?

Expert replies
Post new topic Post Reply
Previous Topic Next Topic
Legendary Member
Posts: 2326
Joined: Mon Jul 28, 2008 3:54 amFollowed by: 2 members
Thanked: 173 times
GMAT Score:710
by gmatmachoman » Tue Apr 06, 2010 1:03 am
Does x = y ?

(1) The average of x and 1/x equals the average of y and 1/ y

.
(2) xy = 1

OA"E
Last edited by gmatmachoman on Tue Apr 06, 2010 12:12 pm, edited 1 time in total.
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Source: — Data Sufficiency |
User avatar
Master | Next Rank: 500 Posts
Posts: 435
Joined: Mon Mar 15, 2010 6:15 amFollowed by: 1 member
Thanked: 32 times

by eaakbari » Tue Apr 06, 2010 1:57 am
Statement one

(x + 1/x) /2 = (y +1/y)/2

(x^2 + 1)/x = (y^2 +1)/y

cross multiplying

x^2y + y = xy^2 + x

x(xy-1)= y(xy-1)

Hence if xy is not equal to -1 then x = y but we dont know whether xy is -1 or not
Hence Insuff

Statemnet two

Tells us xy = 1

It can be 1/3 * 3 which are not equal hence Insuff

Combined
We needed the value of xy -1 which we get from 2 which is zero

Hence Insuff

IMO E
Last edited by eaakbari on Tue Apr 06, 2010 11:28 am, edited 1 time in total.
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Master | Next Rank: 500 Posts
Posts: 148
Joined: Tue Jun 09, 2009 11:06 pm
Thanked: 7 times

by pops » Tue Apr 06, 2010 2:17 am
gmatmachoman wrote:Does x = y ?

(1) The average of x and 1/x equals the average of y and 1/ y

.
(2) xy = 1
statement 1:
x + 1/x = y + 1/y
2 possibilities: x=y or x=1/y. hence insufficient

statement 2:
x=1/y
2 possibilities: if y=1, x=y but if y is anything else x is not equal to y

combining the above two is not giving any new information... if x=1/y then mean of x+1/x will be equal to mean of y+1/y
hence the doubt stays i.e. if y=1, x=y but if y is anything else x is not equal to y

hence both statements are not sufficient to answer !
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
Legendary Member
Posts: 1275
Joined: Thu Sep 21, 2006 11:13 pmFollowed by: 2 members
Location: Arabian Sea
Thanked: 125 times

by ajith » Tue Apr 06, 2010 6:51 am
gmatmachoman wrote:Does x = y ?

(1) The average of x and 1/x equals the average of y and 1/ y

.
(2) xy = 1

2) => y = 1/x

in which case x=y when x=y=1

when x=y=1 1) and 2 are satisfied
when x = 1/2 and y =2 1 and 2 are satisfied

we cant say anything about whether x =y even when both statements are true

so E
Always borrow money from a pessimist, he doesn't expect to be paid back.
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Legendary Member
Posts: 610
Joined: Fri Jan 15, 2010 12:33 amFollowed by: 2 members
Thanked: 47 times

by kstv » Tue Apr 06, 2010 8:10 am
eaakbari wrote:Statement one
(x + 1/x) /2 = (y +1/y)/2
(x^2 + 1)/x = (y^2 +1)/y
cross multiplying
x^2y + y = xy^2 + x
x(xy+1)= y(xy+1)
Hence if xy is not equal to -1 then x = y but we dont know whether xy is -1 or not
Hence Insuff
IMO C
got to recheck the bold part
x²y+y = xy²+x
x²y -x = xy² - y
x(xy-1) = y(xy-1)
from (2) we know xy -1 = 0
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Master | Next Rank: 500 Posts
Posts: 135
Joined: Tue Oct 13, 2009 10:27 am
Thanked: 3 times

by boazkhan » Tue Apr 06, 2010 8:49 am
IMO C -- What is the OA?
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Senior | Next Rank: 100 Posts
Posts: 51
Joined: Tue Apr 14, 2009 1:52 am
Location: Hyderbad,India
Thanked: 3 times
GMAT Score:580

by srinivasarajui » Tue Apr 06, 2010 10:04 am
IMO E what is the OA.
Srinu
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
Master | Next Rank: 500 Posts
Posts: 435
Joined: Mon Mar 15, 2010 6:15 amFollowed by: 1 member
Thanked: 32 times

by eaakbari » Tue Apr 06, 2010 11:25 am
kstv wrote:
eaakbari wrote:Statement one
(x + 1/x) /2 = (y +1/y)/2
(x^2 + 1)/x = (y^2 +1)/y
cross multiplying
x^2y + y = xy^2 + x
x(xy+1)= y(xy+1)
Hence if xy is not equal to -1 then x = y but we dont know whether xy is -1 or not
Hence Insuff
IMO C
got to recheck the bold part
x²y+y = xy²+x
x²y -x = xy² - y
x(xy-1) = y(xy-1)
from (2) we know xy -1 = 0

Thanks for pointing that out. Silly mistakes , Silly mistakes. Edited it.
Answer does change
E
Thanks again kstv

Please give OA gmatmachoman
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Post new topic Post Reply
• Page 1 of 1