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

Exponent Problem - Kinda Tricky!

Expert replies
Post new topic Post Reply
Subscribe topic
Previous Topic Next Topic
Master | Next Rank: 500 Posts
Posts: 266
Joined: Mon Oct 19, 2009 9:46 pm
Thanked: 8 times
GMAT Score:690
by pkw209 » Wed Apr 14, 2010 4:14 pm
Hey guys,

Couldn't figure this one out. An explanation would be great! Thanks.

Image

Image
Top
Join the discussion
Source: — Problem Solving |
Master | Next Rank: 500 Posts
Posts: 216
Joined: Mon Dec 21, 2009 10:26 am
Thanked: 16 times

by student22 » Wed Apr 14, 2010 4:32 pm
I used the equation editor to make the solution as clear as possible. Basically what I did was multiply each of the 3^7 and 3^8 exponents by "1" in order to convert the denominators into the same exponent. Hopefully, it's clear, if not let me know.
Image


The --> arrows just mean, next step...
Top
Join the discussion
Master | Next Rank: 500 Posts
Posts: 266
Joined: Mon Oct 19, 2009 9:46 pm
Thanked: 8 times
GMAT Score:690

by pkw209 » Wed Apr 14, 2010 4:37 pm
That's what I got as well. Pulled this from another source so I thought the answer was E.

Fantastic job and explanation. That type of effort is what makes this site awesome.
Top
Join the discussion
Master | Next Rank: 500 Posts
Posts: 114
Joined: Mon Sep 22, 2008 3:51 am
Thanked: 8 times
GMAT Score:680

by Fiver » Wed Apr 14, 2010 7:12 pm
pkw209 wrote:Hey guys,

Couldn't figure this one out. An explanation would be great! Thanks.

Image

Image
Another way is to apply the formula for the total sum in a GP.

x - (2/3^7 + 2/3^8 + 2/3^9) = 1/3^9
the bold part is a GP with FT as 2/3^9 and common ration as 3
Sum of a GP = FT * (r^n - 1)/ r-1 )
sum = 2/3^9 ( 3^3 - 1) / (3-1)
= 2/3^9 *(26/2) = 26/3^9

Therefore x - 26/3^9 = 1/3^9
x = 27/3^9
x = 1/3^6
Top
Join the discussion
Legendary Member
Posts: 610
Joined: Fri Jan 15, 2010 12:33 amFollowed by: 2 members
Thanked: 47 times

by kstv » Wed Apr 14, 2010 8:24 pm
Multiply by 3^8 it is kinda of a middle value , which makes the calc manageable
3^8X - 2*3 - 2 - 2/3 = 1/3
3^8 X = 6+2+1 = 3²
X = 1/3^6
Top
Join the discussion
User avatar
Legendary Member
Posts: 1560
Joined: Tue Nov 17, 2009 2:38 amFollowed by: 5 members
Thanked: 137 times

by thephoenix » Thu Apr 15, 2010 3:20 am
let 3^7=y
the eqn becomes x-2/y-2/3y-2/9y=1/9y
simplifying
(9xy-18-6-2)/9y=1/9y
or
9xy-18-6-2=1 or
9xy=27
or
x=27/9*3^7=3/3^7=1/3^6
Top
Join the discussion