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 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
Live EA class + 6 months of EA OnDemand
  • Expert-led weekly online sessions
  • EA Masterclass access between classes
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.

130-point 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.

Manhattan GMAT Question

Expert replies
Post new topic Post Reply
Previous Topic Next Topic
Source: — Problem Solving |
User avatar
Site Admin
Posts: 2567
Joined: Thu Jan 01, 2009 10:05 amFollowed by: 550 members
Thanked: 712 times
GMAT Score:770

by DanaJ » Wed Feb 11, 2009 6:02 am
4^4x means 4 raised to the 4x-th power, which cannot be 1600. Doing the prime factorization of 1600 you get that it is equal to (4^3)*(5^2), so it cannot be a power of 4. Therefore IMHO your equation is not correctly written.
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Newbie | Next Rank: 10 Posts
Posts: 6
Joined: Tue Jan 27, 2009 6:37 am
Thanked: 3 times

by jail » Wed Feb 11, 2009 8:23 am
This can be solved:

4^4x = 2^8x and 1600 = 40^2 = (5^2)*(2^6) , therefore

2^8x=(5^2)*(2^6) Multiply both with the power 1/2

2^4x= 5 * 2^3 Thus 2^4x = 40 ---> a

Now we are looking for (4^x–1)^2 which is = 2^4x-4

2^4x-4 = 2^4x * 1/16 Now sustitute with a

40 * 1/16 = 5/2
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Newbie | Next Rank: 10 Posts
Posts: 3
Joined: Mon Jan 19, 2009 8:28 pm

by sastagi » Wed Feb 11, 2009 9:56 am
(4^x-1)^2

= (4)^2x-2

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

= ((4)^2x)/16

=(4)^(4x/2)/16

=[(1600)^(1/2)]/16

=40/16

=5/2
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Master | Next Rank: 500 Posts
Posts: 258
Joined: Thu Aug 07, 2008 5:32 am
Thanked: 16 times

Re: Manhattan GMAT Question

by x2suresh » Wed Feb 11, 2009 10:11 am
gabriel16 wrote:If 4^4x = 1600, what is the value of (4^x–1)^2?


Any help is greatly appreciated. Thanks.
(4^x)^4 =20^4

4^x=20


(4^(x-1))^2 = (4^x/4)^2= (20/4)^2 = 25/4
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Senior | Next Rank: 100 Posts
Posts: 55
Joined: Mon Dec 08, 2008 11:06 am
Thanked: 2 times

by gabriel16 » Wed Feb 11, 2009 10:36 am
Great stuff. I ran across this question on a MGMAT practice test and couldn't figure it out at first. Thanks for your help.
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Master | Next Rank: 500 Posts
Posts: 139
Joined: Wed Oct 22, 2008 4:36 am
Thanked: 17 times

by sacx » Thu Feb 12, 2009 2:27 am
If 4^4x = 1600, what is the value of (4^x–1)^2

4^4x => 4^2x * 4^2x
1600 = > 40 * 40

(4^x–1)^2 = (4^2x)/ 16

= 40/16 => 5/2
SACX
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
Master | Next Rank: 500 Posts
Posts: 319
Joined: Wed Feb 04, 2009 10:32 amFollowed by: 9 members
Location: Delhi
Thanked: 84 times

by sureshbala » Thu Feb 12, 2009 2:36 am
Folks, this was answered earlier....Here is the link

https://www.beatthegmat.com/exponents-pr ... tml#123429
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Post new topic Post Reply
• Page 1 of 1