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

Exponential Equations - Solve for X

Expert replies
Post new topic Post Reply
Subscribe topic
Previous Topic Next Topic
Newbie | Next Rank: 10 Posts
Posts: 2
Joined: Thu May 29, 2008 4:30 am
by Margreter » Mon Aug 04, 2008 6:16 am
I am taking the GMAT in a couple of weeks. I am doing fine so far, but there are these two annoying questions, that, no matter how hard I try - I do not know how to solve! There are apparently some rules concerning exponents I have missed...


1. 5^21 x 4^11 = 2x 10^n.

The answer is n = 21, but have no idea how to get there.


2. 2^x - 2^(x-2) = 3(2^13)

The answer is x= 15, but again....????

I guess it is uneccessary to say that exponents is not my strongest side :=)

Thanks you for all your help!
Top
Join the discussion
Source: — Problem Solving |
Legendary Member
Posts: 829
Joined: Mon Jul 07, 2008 10:09 pmFollowed by: 3 members
Location: INDIA
Thanked: 84 times

by sudhir3127 » Mon Aug 04, 2008 6:29 am
Please use the search option before posting a new question . and make sure u post one question per thread...

1 st question

5^21 * 4^11 = 2*10^n

we can write 4^21 as (2^2)^11 which is 2^22

hence its 5^21* 2^22

we can write 2^22 as 2* 2^21 ( a^m+n = a^m* a^n)

hence its

5^21*2*2^21 which can be written as

2* ( 5*2) 21 ...( a^m * b*m = ab^m)


thus its

2* (10)^21 = 2*10^n

hence n = 21

Hope its clear...
Top
Join the discussion
Legendary Member
Posts: 829
Joined: Mon Jul 07, 2008 10:09 pmFollowed by: 3 members
Location: INDIA
Thanked: 84 times

by sudhir3127 » Mon Aug 04, 2008 6:35 am
2. 2^x -2^(x-2) = 3(2^13)

u shud know that a^m/a^n = a^m-n...

we have to use the above rule in this question

2^x - 2^x/2^2 = 3( 2^13)........... ( 2^(x-2) can be written as 2^x/2^2 using the rule i mentioned

take 2^x common

2^x ( 1-1/4) = 3 (2^13)

2^x(3/4 ) = 3 (2^13)

cancel off 3 on both the sides..

2^x= 4*2^13

4 can be written as 2^2

hence its
2^x = 2^15 ( a^m* a^n = a^m+n )

hence x = 15...
Top
Join the discussion