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

Interesting Geometry Question

Expert replies
Post new topic Post Reply
Subscribe topic
Previous Topic Next Topic
Senior | Next Rank: 100 Posts
Posts: 89
Joined: Wed Mar 13, 2013 3:36 amFollowed by: 1 member
Thanked: 10 times
by killerdrummer » Tue Mar 26, 2013 1:41 am
A 4 cm cube is cut into 1 cm cubes. What is the percentage increase in the surface area after such cutting?

(A) 4%
(B) 166%
(C) 266%
(D) 300%
(E) 400%


Although I have posted answer below but i am still looking for a quick and crisp method. :)

[spoiler]
-----------------------------------------------------------------------------------------------
D
-----------------------------------------------------------------------------------------------
Solution:

Volume of bigger cube(BC) = 4*4*4 = 64
Volume of Smaller CUBE (SC) = 1*1*1 = 1
Therefore we have 64 small cubes

SA = 6 (SIDE)*(SIDE) BC = 96 & SC =64*6= 384
%inc = [(384-96)/96]*100
[/spoiler]
Top
Join the discussion
Source: — Problem Solving |
Junior | Next Rank: 30 Posts
Posts: 16
Joined: Wed Mar 13, 2013 10:17 pmFollowed by: 1 member
Thanked: 2 times

by Alina Ross » Tue Mar 26, 2013 2:35 am
The General solution would be as below:
Solution: 

Volume of bigger cube(BC) = 4*4*4 = 64 
Volume of Smaller CUBE (SC) = 1*1*1 = 1 
Therefore we have 64 small cubes 

SA = 6 (SIDE)*(SIDE) BC = 96 & SC =64*6= 384 
%inc = [(384-96)/96]*100
Top
Join the discussion

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 511
Joined: Wed Aug 11, 2010 9:47 amFollowed by: 86 members
Location: Delhi, India
Thanked: 344 times

by Anju@Gurome » Tue Mar 26, 2013 8:24 am
killerdrummer wrote:A 4 cm cube is cut into 1 cm cubes. What is the percentage increase in the surface area after such cutting?
Total surface area of a cube = (Number of faces)*(Surface area of a face) = 6a², where a is the length of each edge of the cube.

Total surface area of the 4cm cube = 6*(4²) = 6*16 sq. cm
Total surface area of the 1cm cube = 6*(1²) = 6 sq. cm

Number of 1cm cubes = (Volume of 4cm cube)/(Volume of 1cm cube) = 4³/1³ = 4³ = 64

Hence, required percentage = 100*(Total surface area of all the 1cm cubes - Total surface area of the 4cm cube)/(Total surface area of the 4cm cube) = 100*(6*64 - 6*16)/(6*16) = 100*(4 - 1)/1 = 100*3 = 300

The correct answer is D.
Anju Agarwal
Quant Expert, Gurome

Backup Methods : General guide on plugging, estimation etc.
Wavy Curve Method : Solving complex inequalities in a matter of seconds.

§ GMAT with Gurome § Admissions with Gurome § Career Advising with Gurome §
Top
Join the discussion