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 →

Digits

Expert replies
Post new topic Post Reply
Previous Topic Next Topic
Newbie | Next Rank: 10 Posts
Posts: 2
Joined: Tue Oct 25, 2011 4:33 pm
by mbamph2012 » Wed Oct 26, 2011 11:19 am
Can someone please explain this to me.

If xy represents a positive two-digit number, where x and y are single digit integers, which of the following CANNOT be true?
x + y = 9
xy = 9
x - y = 9
y - x = 9
x/y = 9
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Source: — Problem Solving |
User avatar
GMAT Instructor
Posts: 349
Joined: Wed Sep 28, 2011 3:38 pmFollowed by: 54 members
Location: Austin, TX
Thanked: 236 times
GMAT Score:770

by GmatMathPro » Wed Oct 26, 2011 11:58 am
x+y=9.....54
xy=9......91
x-y=9.....90
y-x=9.....impossible
x/y=9.....91

y-x=9 is impossible because the only two digits with a difference of 9 is 9 and 0, so it would have to be that y=9 and x=0, but that would make the number xy, 09 or just 9. But 9 is a one-digit number, not a two-digit number.
Pete Ackley
GMAT Math Pro
Free Online Tutoring Trial
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Newbie | Next Rank: 10 Posts
Posts: 2
Joined: Tue Oct 25, 2011 4:33 pm

by mbamph2012 » Wed Oct 26, 2011 1:27 pm
Ok thanks, I was thinking that in the question it was saying xy=9
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
GMAT Instructor
Posts: 349
Joined: Wed Sep 28, 2011 3:38 pmFollowed by: 54 members
Location: Austin, TX
Thanked: 236 times
GMAT Score:770

by GmatMathPro » Wed Oct 26, 2011 1:33 pm
Yeah it probably could have been written more clearly.
Pete Ackley
GMAT Math Pro
Free Online Tutoring Trial
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Junior | Next Rank: 30 Posts
Posts: 15
Joined: Sun Jul 10, 2011 11:19 pm

by neya » Wed Oct 26, 2011 6:41 pm
Since xy is a positive two-digit number, then xy=9 is it true? Confused.
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
GMAT Instructor
Posts: 349
Joined: Wed Sep 28, 2011 3:38 pmFollowed by: 54 members
Location: Austin, TX
Thanked: 236 times
GMAT Score:770

by GmatMathPro » Wed Oct 26, 2011 7:05 pm
Yeah, the confusing thing is that they use xy to mean two different things in this problem. When they say xy=9 in the answer choices they mean x*y=9. In other words, the ten's digit times the unit's digit equals nine. This is certainly possible if x is 9 and y is 1.

On the other hand, in the question they use xy to represent a two digit integer, where if x=9 and y=1 xy=91, and xy does NOT mean to multiply x and y.

Usually xy would be understood to mean "x times y" but since they define it in a different way in the question, they should really use a more explicit notation for multiplication.

Of course, the writers of a real GMAT question would be careful to avoid this kind of ambiguity.
Pete Ackley
GMAT Math Pro
Free Online Tutoring Trial
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
Senior | Next Rank: 100 Posts
Posts: 47
Joined: Wed Nov 24, 2010 12:57 am
Thanked: 3 times

by Cheese12 » Wed Oct 26, 2011 8:41 pm
even i read xy as "x times y" :|
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Post new topic Post Reply
• Page 1 of 1