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.

Which of the following is the best approximation for 11^11-9

Expert replies
Post new topic Post Reply
Previous Topic Next Topic
User avatar
Elite Legendary Member
Posts: 3991
Joined: Fri Jul 24, 2015 2:28 amFollowed by: 37 members
Location: Las Vegas, USA
Thanked: 19 times
by Max@Math Revolution » Tue Aug 21, 2018 2:33 am

Timer

00:00

Answers

A

B

C

D

E

Stats

Difficulty—

[Math Revolution GMAT math practice question]

Which of the following is the best approximation for 11^11-9^9?

A. 11^8
B. 11^9
C. 11^10
D. 11^11
E. 11^12
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Source: — Problem Solving |
Master | Next Rank: 500 Posts
Posts: 416
Joined: Thu Oct 15, 2009 11:52 am
Thanked: 27 times

by regor60 » Tue Aug 21, 2018 7:10 am
Max@Math Revolution wrote:[Math Revolution GMAT math practice question]

Which of the following is the best approximation for 11^11-9^9?

A. 11^8
B. 11^9
C. 11^10
D. 11^11
E. 11^12
11 = 1.1 x 10
9 = .9 x 10

Reformulating:

(1.1x10)^11 - (.9 x 10)^9 = 11^11 - 9^9

Splitting out the parts:

(1.1 x 10)^ 11 = 1.1^11 x 10^11 and (.9 x 10)^9 = .9^9 x 10^9

Factoring out the 10^9:

10^9(1.1^11 x 10^2 - ,9^9 x 1)

Now .9^9 is essentially 0, so this now reduces to 10^9(1.1^11 x 10^2) = 1.1^11 x 10^11 = [spoiler] 11^11,D[/spoiler]
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
GMAT Instructor
Posts: 15539
Joined: Tue May 25, 2010 12:04 pmFollowed by: 1906 members
Location: New York, NY
Thanked: 13060 times
GMAT Score:790

by GMATGuruNY » Tue Aug 21, 2018 7:23 am
Max@Math Revolution wrote:[Math Revolution GMAT math practice question]

Which of the following is the best approximation for 11^11-9^9?

A. 11^8
B. 11^9
C. 11^10
D. 11^11
E. 11^12
Since the answer choices are very spread out, our approximation does not have to very exact.
11¹¹−9�
= 11¹¹− (11−2)�
≈ 11¹¹ − 11�
= 11�(11²−1)
≈ (11�)(11²)
= 11¹¹

The correct answer is D.
Private tutor exclusively for the GMAT and GRE, with over 20 years of experience.
Followed here and elsewhere by over 1900 test-takers.
I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.

As a tutor, I don't simply teach you how I would approach problems.
I unlock the best way for YOU to solve problems.

For more information, please email me (Mitch Hunt) at [email protected].
Student Review #1
Student Review #2
Student Review #3
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
GMAT Instructor
Posts: 15539
Joined: Tue May 25, 2010 12:04 pmFollowed by: 1906 members
Location: New York, NY
Thanked: 13060 times
GMAT Score:790

by GMATGuruNY » Tue Aug 21, 2018 7:48 am
Max@Math Revolution wrote:[Math Revolution GMAT math practice question]

Which of the following is the best approximation for 11^11-9^9?

A. 11^8
B. 11^9
C. 11^10
D. 11^11
E. 11^12
Another approach:
10¹¹ (100,000,000,000) is 100 TIMES the value of 10� (1,000,000,000).
Implication:
11¹¹ must be MORE THAN 100 TIMES the value of 9�.
Since 9� is so small when compared to 11¹¹, we can ignore the value of 9� when we approximate:
11¹¹ - 9� ≈ 11¹¹

The correct answer is D.
Private tutor exclusively for the GMAT and GRE, with over 20 years of experience.
Followed here and elsewhere by over 1900 test-takers.
I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.

As a tutor, I don't simply teach you how I would approach problems.
I unlock the best way for YOU to solve problems.

For more information, please email me (Mitch Hunt) at [email protected].
Student Review #1
Student Review #2
Student Review #3
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
Elite Legendary Member
Posts: 3991
Joined: Fri Jul 24, 2015 2:28 amFollowed by: 37 members
Location: Las Vegas, USA
Thanked: 19 times

by Max@Math Revolution » Thu Aug 23, 2018 1:07 am
=>

9^9 is much smaller than 11^11.
Thus, 11^11-9^9 is closest to 11^11.

Therefore, the answer is D.
Answer: D
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 8211
Joined: Sat Apr 25, 2015 10:56 amFollowed by: 29 members
Location: Los Angeles, CA
Thanked: 43 times

by Scott@TargetTestPrep » Thu Aug 23, 2018 4:12 pm
Max@Math Revolution wrote:[Math Revolution GMAT math practice question]

Which of the following is the best approximation for 11^11-9^9?

A. 11^8
B. 11^9
C. 11^10
D. 11^11
E. 11^12

Each term is a large number, however, 9^9 is much smaller than 11^11 when it's compared to 11^11. Therefore, the difference will still be approximately 11^11.

(Note: If you can't see that 9^9 is much smaller than 11^11, let's compare their ratio:

9^9/11^11 < 10^9/10^11= 1/10^2 = 1/100 = 1%

We see that 9^9 is less than 1% of 11^11, that is, their difference, 11^11 - 9^9 will be more than 99% of 11^11.)

Alternate Solution:

Let's approximate 9 to 11:

11^11 - 9^9 ≈ 11^11 - 11^9 = 11^9(11^2 - 1)

We see that 11^2 - 1 is approximately 11^2; therefore 11^11 - 9^9 is approximately 11^9 * 11^2 = 11^11.

Answer: D

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
Post new topic Post Reply
• Page 1 of 1