Last visit was: 23 May 2024, 09:46 It is currently 23 May 2024, 09:46
Close
GMAT Club Daily Prep
Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track
Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History
Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.
Close
Request Expert Reply
Confirm Cancel
SORT BY:
Date
Tags:
Show Tags
Hide Tags
Math Expert
Joined: 02 Sep 2009
Posts: 93418
Own Kudos [?]: 626072 [2]
Given Kudos: 81940
Send PM
Intern
Intern
Joined: 12 Jul 2019
Posts: 7
Own Kudos [?]: 3 [0]
Given Kudos: 82
Location: Cote d'Ivoire
GPA: 3.34
WE:Accounting (Accounting)
Send PM
Board of Directors
Joined: 11 Jun 2011
Status:QA & VA Forum Moderator
Posts: 6067
Own Kudos [?]: 4707 [1]
Given Kudos: 463
Location: India
GPA: 3.5
WE:Business Development (Commercial Banking)
Send PM
Manager
Manager
Joined: 10 Oct 2017
Posts: 67
Own Kudos [?]: 54 [0]
Given Kudos: 14
Send PM
Re: If cube X has an edge of length e and cube Y has an edge of length e + [#permalink]
Option A.
TSA Cube X = 6 e^2
TSA Cube Y = 6 ( e + 1 )^2 = 6e^2 + 12e + 6.
Difference = 6e^2 + 12e + 6 - 6e^2
12e + 6
GMAT Club Legend
GMAT Club Legend
Joined: 12 Sep 2015
Posts: 6817
Own Kudos [?]: 30306 [1]
Given Kudos: 799
Location: Canada
Send PM
Re: If cube X has an edge of length e and cube Y has an edge of length e + [#permalink]
1
Kudos
Expert Reply
Top Contributor
Bunuel wrote:
If cube X has an edge of length e and cube Y has an edge of length e + 1, how much greater is the total surface area of cube Y than that of cube X ?

A. 12e + 6
B. 6(e + 1)²
C. e + 1
D. e
E. 1
PS21177


These kinds of questions (Variables in the Answer Choices - VIACs) can be answered algebraically or using the INPUT-OUTPUT approach.
The posters above have solved the question algebraically, so let's use the INPUT-OUTPUT approach.

Let's say e = 3

Cube X
Each edge has length 3
Since each face of the cube is a SQUARE, the area of ONE face = 3² = 9
So, the area of all SIX faces = (6)(9) = 54

Cube Y
Each edge has length 3 + 1. So, each edge has length 4
Since each face of the cube is a SQUARE, the area of ONE face = 4² = 16
So, the area of all SIX faces = (6)(16) = 96

How much greater is the total surface area of cube Y than that of cube X?
Difference = 96 - 54 = 42

So, when we INPUT e = 3, the answer to the question (i.e., the OUTPUT) is 42

Now we'll examine each answer choice, to see which one yields and output of 42 when we replace e with 3

We get:
A. 12(3) + 6 = 42 Great! Keep.
B. 6(3 + 1)² = 24. We want an output of 42. ELIMINATE B
C. 3 + 1 = 4. We want an output of 42. ELIMINATE C
D. 3 = 3. We want an output of 42. ELIMINATE D
E. 1 = 1. We want an output of 42. ELIMINATE E

Answer: A

Cheers,
Brent
IESE School Moderator
Joined: 11 Feb 2019
Posts: 271
Own Kudos [?]: 171 [0]
Given Kudos: 53
Send PM
If cube X has an edge of length e and cube Y has an edge of length e + [#permalink]
SA for cube = 6 * (side)^2
SA for X = 6e^2
SQ for Y = 6(e+1)^2

SA for Y - SA for X = 6(e+1)^2 - 6e^2 = 6(e^2 + 2e + 1) -6e^2 = 12e + 6

Hence A
Target Test Prep Representative
Joined: 14 Oct 2015
Status:Founder & CEO
Affiliations: Target Test Prep
Posts: 18895
Own Kudos [?]: 22304 [0]
Given Kudos: 285
Location: United States (CA)
Send PM
Re: If cube X has an edge of length e and cube Y has an edge of length e + [#permalink]
Expert Reply
Bunuel wrote:
If cube X has an edge of length e and cube Y has an edge of length e + 1, how much greater is the total surface area of cube Y than that of cube X ?

A. 12e + 6
B. 6(e + 1)2
C. e + 1
D. e
E. 1


PS21177


Solution:

The total surface area of cube Y is 6(e + 1)^2 = 6(e^2 + 2e + 1) = 6e^2 + 12e + 6.

The total surface area of cube X is 6e^2.

Therefore, the total surface area of cube Y exceeds that of cube X by 12e + 6.

Answer: A
Intern
Intern
Joined: 07 Feb 2022
Posts: 23
Own Kudos [?]: 12 [0]
Given Kudos: 166
Send PM
If cube X has an edge of length e and cube Y has an edge of length e + [#permalink]
ScottTargetTestPrep wrote:
Bunuel wrote:
If cube X has an edge of length e and cube Y has an edge of length e + 1, how much greater is the total surface area of cube Y than that of cube X ?

A. 12e + 6
B. 6(e + 1)2
C. e + 1
D. e
E. 1


PS21177


Solution:

The total surface area of cube Y is 6(e + 1)^2 = 6(e^2 + 2e + 1) = 6e^2 + 12e + 6.

The total surface area of cube X is 6e^2.

Therefore, the total surface area of cube Y exceeds that of cube X by 12e + 6.

Answer: A


could you please explain the difference between "how much greater" and "how many greater"?
GMAT Club Bot
If cube X has an edge of length e and cube Y has an edge of length e + [#permalink]
Moderator:
Math Expert
93419 posts