Live GMAT classes with Target Test Prep start Nov 21 and Nov 22. First class free.

See classes
Target Test Prep · GMAT

Choose how you want to prepare

Learn live with an expert or move at your own pace. Every option includes the complete TTP study system.

Newsweek Readers’ Choice Awards 2026 winner: Target Test Prep, #1 Test Prep

Target Test Prep was voted #1 Best Test Prep in the 2026 Newsweek Readers’ Choice™ Awards.

★★★★★5.0563 reviews
GMATLiveTeachStarts Nov 22
Josh Braslow, Target Test Prep GMAT expert
LIVE ONLINE CLASSES

Get Ready for GMAT Test Day Faster with Live Online Classes

with Josh Braslow, 20+ years in test prep

Nov 22 · Josh Braslow
Sun · 9:30 AM to 12:30 PM ET
Included
40 hours of live online classes + 6 months of TTP OnDemand
  • Attend the first class for free
  • Every class is recorded, so you never fall behind
View classes & enroll
Limited seats availableTarget Test Prep
EALiveTeachOnDemandStart anytime
EXECUTIVE ASSESSMENT

Target Test Prep EA OnDemand

Self-paced EA prep. Study on your schedule.

EXECUTIVE ASSESSMENT

with

165+ EA score guarantee
$05-day trial no automatic billing
Schedule
Included
40 hours of live online classes plus six months of access to the complete TTP EA OnDemand course.
  • 165+ EA Score Guarantee
  • 4,100+ Quant, Verbal, and Integrated Reasoning practice questions
  • 400+ hours of in-depth video lessons
  • 3,000+ step-by-step video solutions
View EA class & enroll Start free 5-day trial
Limited cohort · enrollment openTrial includes full course accessTarget Test Prep
GMATOnDemandStart anytime
SELF-PACED MASTERCLASS

Target Test Prep GMAT OnDemand

Complete access from day one. Study on your schedule.

715+ score guarantee
$0to start then $127/mo
  • Personalized study plan and analytics
  • Thousands of lessons and practice questions
Start free 5-day trial
Read 563 reviewsTarget Test Prep

CANNOT be the sum

Expert replies
Post new topic Post Reply
Subscribe topic
Previous Topic Next Topic
Master | Next Rank: 500 Posts
Posts: 489
Joined: Tue Jul 05, 2011 11:10 amFollowed by: 5 members
Thanked: 28 times
by gmatblood » Mon Oct 31, 2011 10:30 am
If the two-digit integers M and N are positive and have
the same digits, but in reverse order, which of the
following CANNOT be the sum of M and N ?
(A) 181
(B) 165
(C) 121
(D) 99
(E) 44

Would like to know if there is any shortcut to check it!
Top
Join the discussion
Source: — Problem Solving |
Newbie | Next Rank: 10 Posts
Posts: 8
Joined: Mon Sep 26, 2011 9:12 amFollowed by: 3 members
Thanked: 3 times
GMAT Score:710

by ripulgupta » Mon Oct 31, 2011 11:08 am
As we are adding two two-digit numbers and both the number contain the same digits but in reverse order. The last two digits of there addition have to be either same or tens digit can be one more than the units digits. This condition is true for all the options except A. Thus the solution.
Top
Join the discussion
Legendary Member
Posts: 966
Joined: Sat Jan 02, 2010 8:06 amFollowed by: 21 members
Thanked: 230 times

by shankar.ashwin » Mon Oct 31, 2011 11:09 am
Well it should be a multiple of 11.
10X+Y +10Y+X = 11(X+Y) A is not.
Top
Join the discussion
Master | Next Rank: 500 Posts
Posts: 489
Joined: Tue Jul 05, 2011 11:10 amFollowed by: 5 members
Thanked: 28 times

by gmatblood » Mon Oct 31, 2011 11:14 am
shankar.ashwin wrote:Well it should be a multiple of 11.
10X+Y +10Y+X = 11(X+Y) A is not.
Is this condition valid all the time?
Top
Join the discussion
Master | Next Rank: 500 Posts
Posts: 489
Joined: Tue Jul 05, 2011 11:10 amFollowed by: 5 members
Thanked: 28 times

by gmatblood » Mon Oct 31, 2011 11:14 am
ripulgupta wrote:As we are adding two two-digit numbers and both the number contain the same digits but in reverse order. The last two digits of there addition have to be either same or tens digit can be one more than the units digits. This condition is true for all the options except A. Thus the solution.
Is this a valid condition! Thanks anyways :)
Top
Join the discussion
Legendary Member
Posts: 966
Joined: Sat Jan 02, 2010 8:06 amFollowed by: 21 members
Thanked: 230 times

by shankar.ashwin » Mon Oct 31, 2011 11:24 am
Yup, it is. Similarly if the digits of 2 numbers are reversed and subtracted,

10X+Y -10Y-X = 9(X-Y), the number would be a multiple of 9.

gmatblood wrote:
shankar.ashwin wrote:Well it should be a multiple of 11.
10X+Y +10Y+X = 11(X+Y) A is not.
Is this condition valid all the time?
Top
Join the discussion