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

Redeem

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.

★★★★★5.0559 reviews
GMATLiveTeach Starts Oct 17
Chris Peckover, Target Test Prep GMAT expert
LIVE ONLINE CLASSES

Get Ready for GMAT Test Day Faster with Live Online Classes

with Chris Peckover, 100th-Percentile GMAT Scorer

Oct 17 · Chris Peckover
Sat · 11:00 AM to 2:00 PM ET
Oct 20 · Chris Peckover
Tue, Thu · 8:00 to 10:00 PM ET
Oct 25 · Josh Braslow
Sun · 1:00 to 4:00 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
EALiveTeachOnDemand 5 seats left Start anytime
EXECUTIVE ASSESSMENT

Target Test Prep EA OnDemand

Self-paced EA prep. Study on your schedule.

Logan Thompson
EXECUTIVE ASSESSMENT

Sep 6 to Dec 6, 2026

with Logan Thompson

165+ EA score guarantee
$05-day trial no automatic billing
Schedule
Sun · 9:30 AM to 12:30 PM ET
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
GMATOnDemand Start 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 559 reviewsTarget Test Prep

Compare the format, schedule, and included access before enrolling. Prices and seat counts shown reflect the supplied offer details.

DS - Arithmetic, Algebra ------- Problem

Expert replies
Post new topic Post Reply
Previous Topic Next Topic
User avatar
Newbie | Next Rank: 10 Posts
Posts: 9
Joined: Sun May 31, 2015 1:45 pm
by minihobel » Wed Jun 10, 2015 4:54 am
Hi!

I just ran over this question in OG - QR: DS part question 120.:

Is 1/a-b < b-a ?

(1) a < b
(2) never mind

It's just about (1)

They say: From this, it is known that 1/a-b is negative and b-a is positive. Therefore, 1/a-b < b-a SUFFICIENT.

BUT:
it is not said that a and/or b is positive/negative, so let's assume:
a= -50
b=-100

=> 1/a-b = 1/(-50)-(-100) = 1/50
=> b-a = (-100) - (-50) = -50


So how is (1) sufficient? Thanks in advance!
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Source: — Data Sufficiency |
User avatar
Legendary Member
Posts: 2663
Joined: Wed Jan 14, 2015 8:25 amFollowed by: 128 members
Location: Boston, MA
Thanked: 1153 times
GMAT Score:770

by DavidG@VeritasPrep » Wed Jun 10, 2015 5:14 am
Is 1/a-b < b-a ?

(1) a < b
(2) never mind

It's just about (1)

They say: From this, it is known that 1/a-b is negative and b-a is positive. Therefore, 1/a-b < b-a SUFFICIENT.

BUT:
it is not said that a and/or b is positive/negative, so let's assume:
a= -50
b=-100
You have to abide by the condition of the statement. We're told that a<b, so we wouldn't be allowed to test a = -50 and b = -100, because a would be greater in this case. Think of it this way. If a<b, we can subtract b from both sides to get a-b<0. If you multiply both sides by (-1) the sign will flip, and we'll have b - a> 0.

If a- b< 0, 1/(a-b) will be negative. Obviously, this will be less than b -a, which we know is positive.
Veritas Prep | GMAT Instructor

Veritas Prep Reviews
Save $100 off any live Veritas Prep GMAT Course
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 16207
Joined: Mon Dec 08, 2008 6:26 pmFollowed by: 1268 members
Location: Vancouver, BC
Thanked: 5254 times
GMAT Score:770

by Brent@GMATPrepNow » Wed Jun 10, 2015 6:42 am
Is 1/(a-b) < b-a?

1) a < b

Target question: Is 1/(a-b) < b-a?

Statement 1: a < b
If a < b, then a-b is negative, which means 1/(a-b) is NEGATIVE.
Also, if a < b, then b-a is POSITIVE.
A NEGATIVE number is always less than a POSITIVE number, so it must be the case that 1/(a-b) < b-a
Since we can answer the target question with certainty, statement 1 is SUFFICIENT

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
Image
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
Newbie | Next Rank: 10 Posts
Posts: 9
Joined: Sun May 31, 2015 1:45 pm

by minihobel » Wed Jun 10, 2015 6:47 am
after reading this, i feel pretty stupid right now.
Sorry for the question... I should have read more carefully.

Thanks guys. Your help is much appreciated!!
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Legendary Member
Posts: 518
Joined: Tue May 12, 2015 8:25 pm
Thanked: 10 times

by nikhilgmat31 » Fri Jun 12, 2015 3:40 am
what is Case 2 in this question ?
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
Legendary Member
Posts: 2663
Joined: Wed Jan 14, 2015 8:25 amFollowed by: 128 members
Location: Boston, MA
Thanked: 1153 times
GMAT Score:770

by DavidG@VeritasPrep » Fri Jun 12, 2015 3:56 am
what is Case 2 in this question ?
Statement 2: 1<|a-b|

(And you can see pretty quickly that this statement alone will not be sufficient.)
Case 1: a=4 b = 2; 1/(a-b) is greater than b-a, so answer is YES.
Case 2: a = 2 b = 4 1/(a-b) is not greater than b-a, so answer is NO.
Veritas Prep | GMAT Instructor

Veritas Prep Reviews
Save $100 off any live Veritas Prep GMAT Course
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Post new topic Post Reply
• Page 1 of 1