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
Vote for Target Test Prep, Newsweek Readers’ Choice Awards 2026
NEWSWEEK READERS’ CHOICE 2026

BIG NEWS! Target Test Prep has been nominated, and they’d love your vote!

TTP has worked incredibly hard to build the best test prep experience possible, and winning Newsweek’s 2026 Readers’ Choice Award for Best Test Prep would mean a lot to them. If TTP has helped you, they’d be incredibly grateful for your vote. You can vote once each day through September 9.

Vote for TTP
GMATLiveTeach 7 seats left
Chris Peckover
NEXT LIVE COHORT

Oct 13 to Jan 7, 2027

with Chris Peckover

Schedule
Tue, Thu · 8:00 to 10:00 PM ET
Included
40 live hours + 6 months of GMAT OnDemand
  • Live instruction and real-time questions
  • Class recordings and assigned practice
View class & enroll
Limited cohort · enrollment openTarget Test Prep
EALiveTeach 5 seats left
Logan Thompson
EXECUTIVE ASSESSMENT

Sep 6 to Dec 6, 2026

with Logan Thompson

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
Limited cohort · enrollment openTarget 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.

Please can you explain the reasoning behind this?

Expert replies
Post new topic Post Reply
Previous Topic Next Topic
Source: — Problem Solving |
User avatar
GMAT Instructor
Posts: 3225
Joined: Tue Jan 08, 2008 2:40 pmFollowed by: 614 members
Location: Toronto
Thanked: 1710 times
GMAT Score:800

by Stuart@KaplanGMAT » Fri Dec 20, 2013 12:44 pm
shibotta23 wrote:As x increases from 165 to 166, which of the following must increase?

I. 2x-5

II. 1-1/x

III. 1/x squared - x

a) I only
b)III only
c)I and II
d)I and III
e)II and III
Hi!

We're told that x is positive and increasing and we're asked to determine which of 3 expressions will increase along with x.

Here's something to remember: the GMAT is not trying to be your friend, but it is trying to see how clever you are. So, we're always using our cleverness to outwit the test and turn complex questions into simpler ones.

How can we do so on this question? By recognizing that "165 to 166" is an arbitrary range. We can make our lives much easier by saying that x is increasing from 5 to 6 instead, then using those numbers to test the choices.

(I) looks simplest, so let's start there.

If x=5, then 2x-5 = 10-5=5
If x=6, then 2x-5 = 12-5=7

Did (I) increase? YES. Eliminate (b) and (e), since they don't include (I).

(As an aside: the "-5" is irrelevant, since it's a constant and has no impact on whether that expression grows, so we could have just tested "2x" instead.)

Our 3 remaining choices are I only, I and II and I and III. Not much help there, so let's test II next, since it seems simpler than III.

(II) 1 - 1/x

If x = 5, then we get 1 - 1/5 = 4/5
If x = 6, then we get 1 - 1/6 = 5/6

Is 5/6 > 4/5? YES. So, x is increasing once again, which means that (II) is also a winner.

(As another aside, 1 is constant so we could have ignored it and only tested "-1/x"... but you have to remember to include the negative sign, so this one may be easier to test by leaving the 1 in there.)

Only one choice includes both I and II... choose (C)!
Image

Stuart Kovinsky | Kaplan GMAT Faculty | Toronto

Kaplan Exclusive: The Official Test Day Experience | Ready to Take a Free Practice Test? | Kaplan/Beat the GMAT Member Discount
BTG100 for $100 off a full course
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 8183
Joined: Sat Apr 25, 2015 10:56 amFollowed by: 29 members
Location: Los Angeles, CA
Thanked: 43 times

by Scott@TargetTestPrep » Sat Jul 18, 2015 6:49 pm
shibotta23 wrote:As x increases from 165 to 166, which of the following must increase?

I. 2x-5

II. 1-1/x

III. 1/x squared - x

a) I only
b)III only
c)I and II
d)I and III
e)II and III
Solution:

Before jumping into this problem using the numbers provided, we must analyze what is really being tested here. We are really being asked what happens when we increase a positive integer by a value of 1. Using 165 and 166 is cumbersome, so we will use two much smaller numbers, 2 and 3. We can now rephrase the question:

As x increases from 2 to 3, which of the following must increase?

Let's test the new numbers for each Roman numeral.

I. 2x - 5

When x = 2:

2(2) - 5 = -1

When x = 3:

2(3) - 5 = 1

This DOES increase. Roman numeral I is correct. We can eliminate answer choices B and E.

II. 1 - 1/x

When x = 2:

1 - 1/2 = 1/2

When x = 3:

1 - 1/3 = 2/3

This DOES increase. Roman numeral II is also correct. We can eliminate answer choices A and D. Although we know that the answer must be C, let's check Roman number III anyways.

III. 1/(x^2 - x)

When x = 2:

1/(2^2 - 2)

1/(4 - 2) = 1/2

When x = 3:

1/(3^2 - 3)

1/(9 - 3) = 1/6

This DOES NOT increase. Roman numeral III is not correct.

Thus, only I and II are correct.

Answer: C

Scott Woodbury-Stewart
Founder and CEO
[email protected]

Image

See why Target Test Prep is rated 5 out of 5 stars on BEAT the GMAT. Read our reviews

ImageImage
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY

GMAT/MBA Expert

User avatar
Elite Legendary Member
Posts: 10392
Joined: Sun Jun 23, 2013 6:38 pmFollowed by: 511 members
Location: Palo Alto, CA
Thanked: 2867 times
GMAT Score:800

by [email protected] » Sun Jul 19, 2015 6:21 am
Hi All,

Roman Numeral questions are relatively rare on Test Day (you'll likely see just 1 in the Quant section), but they are almost always designed around Number Properties and logic 'shortcuts'...

Here, we're told that X increase from 165 to 166. We're asked which of the following MUST increase. While this prompt might appear 'calculation heavy', you can actually solve it WITHOUT doing calculations (and paying attention to the answer choices).

I. 2X - 5

The "-5" has the same 'math effect', regardless of what X is: the '-5' reduces the value by 5. So as X goes from 165 to 166, 2X gets BIGGER. Since the '-5' has the same effect, 2X-5 definitely gets bigger as X increases from 165 to 166.
Roman Numeral 1 INCREASES
Eliminate Answers B and E.

II. 1 - 1/X

As the denominator of a fraction gets BIGGER, the fraction gets SMALLER. Thus, 1/165 > 1/166. The "1" in this calculation is constant, so subtracting a SMALLER fraction from it will lead to a BIGGER result. As X increases from 165 to 166, 1/X gets SMALLER, so 1-(1/X) definitely gets bigger.
Roman Numeral 2 INCREASES
Eliminate Answers A and D.

There's only one answer remaining (and we don't even have to deal with Roman Numeral 3)...

Final Answer: C

GMAT assassins aren't born, they're made,
Rich
Contact Rich at [email protected]
Image
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 » Wed Jul 29, 2015 4:47 am
Answer is C by substituting values & subtract 2 values.
It answer is positive than second one is greater

It answer is negative than second one is fewer.
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Post new topic Post Reply
• Page 1 of 1