It is currently 14 Dec 2017, 13:15

# Decision(s) Day!:

CHAT Rooms | Wharton R1 | Stanford R1 | Tuck R1 | Ross R1 | Haas R1 | UCLA R1

### 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

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

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# What is the ratio of the surface area of a cube to the surfa

Author Message
TAGS:

### Hide Tags

Director
Status: Finally Done. Admitted in Kellogg for 2015 intake
Joined: 25 Jun 2011
Posts: 531

Kudos [?]: 4317 [1], given: 217

Location: United Kingdom
GMAT 1: 730 Q49 V45
GPA: 2.9
WE: Information Technology (Consulting)
What is the ratio of the surface area of a cube to the surfa [#permalink]

### Show Tags

12 Feb 2012, 20:33
1
KUDOS
4
This post was
BOOKMARKED
00:00

Difficulty:

35% (medium)

Question Stats:

60% (01:06) correct 40% (00:46) wrong based on 310 sessions

### HideShow timer Statistics

What is the ratio of the surface area of a cube to the surface area of a rectangular solid identical to the cube in all ways except that its length has been doubled?

A. 1/4
B. 3/8
C. 1/2
D. 3/5
E. 2
[Reveal] Spoiler: OA

_________________

Best Regards,
E.

MGMAT 1 --> 530
MGMAT 2--> 640
MGMAT 3 ---> 610
GMAT ==> 730

Kudos [?]: 4317 [1], given: 217

Manager
Joined: 31 Jan 2012
Posts: 73

Kudos [?]: 27 [2], given: 2

Re: Surface area of a cube [#permalink]

### Show Tags

12 Feb 2012, 20:41
2
KUDOS
Let X be the side of the cube. Therefore X^2*6= surface area.

the rectangle is the same other than length is 2X. The width and height are the same as the cube. 2*W*H+2*W*L+2*H*L= 2X^2+4X^2+4X^2= 10X^2.

6X^2/10X^2 = 3/5.

Kudos [?]: 27 [2], given: 2

Math Expert
Joined: 02 Sep 2009
Posts: 42607

Kudos [?]: 135655 [3], given: 12705

Re: What is the ratio of the surface area of a cube to the [#permalink]

### Show Tags

13 Feb 2012, 05:25
3
KUDOS
Expert's post
3
This post was
BOOKMARKED
enigma123 wrote:
What is the ratio of the surface area of a cube to the surface area of a rectangular solid identical to the cube in all ways except that its length has been doubled?

A)¼
B)3/8
C)½
D)3/5
E)2

Any idea how to solve these guys?

30 second approach:
A cube has 6 faces, suppose each has an area of 1, so surface area of the cube will be 6;

A rectangular solid identical to the cube in all ways except that its length has been doubled is just complicated way of saying that the rectangular solid is built with two cubes, hence it has 4+4+2=10 faces of a little cube (just imagine to cubes put one on another) and thus the surface area of the rectangular solid will be 10;

Ratio: 6/10=3/5.

_________________

Kudos [?]: 135655 [3], given: 12705

Intern
Joined: 16 Dec 2011
Posts: 46

Kudos [?]: 7 [0], given: 12

GMAT Date: 04-23-2012
Re: What is the ratio of the surface area of a cube to the [#permalink]

### Show Tags

23 Feb 2012, 05:57
surface area of Cube = 6sidesqr
surface area of rectangular soild = 2( lb + bh+ hl)
assume side of cube is X
its surface area is 6Xsqr
surface area of Recatngular solid is = 10Xsqr ( 2( 2Xsqr+Xsqr +2Xsqr))
take ratio of these two we will get 6/10 = 3/5

Kudos [?]: 7 [0], given: 12

Math Expert
Joined: 02 Sep 2009
Posts: 42607

Kudos [?]: 135655 [0], given: 12705

Re: What is the ratio of the surface area of a cube to the [#permalink]

### Show Tags

27 May 2013, 04:51
Bumping for review and further discussion.
_________________

Kudos [?]: 135655 [0], given: 12705

Manager
Joined: 09 May 2013
Posts: 54

Kudos [?]: 15 [0], given: 12

Re: What is the ratio of the surface area of a cube to the [#permalink]

### Show Tags

22 Jun 2013, 00:56
Bunuel wrote:
enigma123 wrote:
What is the ratio of the surface area of a cube to the surface area of a rectangular solid identical to the cube in all ways except that its length has been doubled?

A)¼
B)3/8
C)½
D)3/5
E)2

Any idea how to solve these guys?

30 second approach:
A cube has 6 faces, suppose each has an area of 1, so surface area of the cube will be 6;

A rectangular solid identical to the cube in all ways except that its length has been doubled is just complicated way of saying that the rectangular solid is built with two cubes, hence it has 4+4+2=10 faces of a little cube (just imagine to cubes put one on another) and thus the surface area of the rectangular solid will be 10;

Ratio: 6/10=3/5.

why "4+4+2" if there are two cubes than it should be "4+4" = 8 faces

Kudos [?]: 15 [0], given: 12

Math Expert
Joined: 02 Sep 2009
Posts: 42607

Kudos [?]: 135655 [0], given: 12705

Re: What is the ratio of the surface area of a cube to the [#permalink]

### Show Tags

22 Jun 2013, 02:31
WarriorGmat wrote:
Bunuel wrote:
enigma123 wrote:
What is the ratio of the surface area of a cube to the surface area of a rectangular solid identical to the cube in all ways except that its length has been doubled?

A)¼
B)3/8
C)½
D)3/5
E)2

Any idea how to solve these guys?

30 second approach:
A cube has 6 faces, suppose each has an area of 1, so surface area of the cube will be 6;

A rectangular solid identical to the cube in all ways except that its length has been doubled is just complicated way of saying that the rectangular solid is built with two cubes, hence it has 4+4+2=10 faces of a little cube (just imagine to cubes put one on another) and thus the surface area of the rectangular solid will be 10;

Ratio: 6/10=3/5.

why "4+4+2" if there are two cubes than it should be "4+4" = 8 faces

Plus 2 faces on the top and bottom. Put two dice one on another and see how many faces will it have.
_________________

Kudos [?]: 135655 [0], given: 12705

Manager
Joined: 07 May 2013
Posts: 107

Kudos [?]: 30 [0], given: 1

Re: What is the ratio of the surface area of a cube to the surfa [#permalink]

### Show Tags

14 Nov 2013, 19:12
$$\frac{6S^2}{2(lb+bh+hl)}$$=$$\frac{6x^2}{2(2x^2+x^2+2x^2)}$$=$$\frac{6x^2}{10x^2}$$=$$\frac{3}{5}$$

Kudos [?]: 30 [0], given: 1

Manager
Joined: 07 May 2013
Posts: 107

Kudos [?]: 30 [0], given: 1

Re: What is the ratio of the surface area of a cube to the surfa [#permalink]

### Show Tags

14 Nov 2013, 19:17
Do not get confused as to why I took x. Let side of the cube be x. He says length is doubled. So, l=2x. However, b and h remain unchanged. So, b=h=x.

Kudos [?]: 30 [0], given: 1

SVP
Status: The Best Or Nothing
Joined: 27 Dec 2012
Posts: 1849

Kudos [?]: 2788 [1], given: 193

Location: India
Concentration: General Management, Technology
WE: Information Technology (Computer Software)
Re: What is the ratio of the surface area of a cube to the surfa [#permalink]

### Show Tags

27 Mar 2014, 01:09
1
KUDOS
Area of cube = $$a^2 + a^2 + a^2 + a^2 + a^2 + a^2 = 6 a^2$$

When one of the dimension is doubled, it has impact on 4 sides (rest 2 remains same)

Look at the diagram

Area of rectangular solid $$= a^2 + a^2 + 2 a^2 + 2 a^2 + 2 a^2 + 2 a^2 = 10 a^2$$

Ratio $$= \frac{6 a^2}{10 a^2} = \frac{3}{5}$$

Attachments

cub.jpg [ 22.23 KiB | Viewed 8829 times ]

_________________

Kindly press "+1 Kudos" to appreciate

Kudos [?]: 2788 [1], given: 193

Current Student
Joined: 06 Sep 2013
Posts: 1965

Kudos [?]: 759 [0], given: 355

Concentration: Finance
Re: What is the ratio of the surface area of a cube to the surfa [#permalink]

### Show Tags

31 Mar 2014, 07:35
Hi All,

Let's assume leg of cube is 1 then surface area will be 6(1)^2=6. Now, rectangular solid will be (2)(1)(1), The area of the solid 2(ab+ac+bc) where a=2, b=1 and c=1. Thus its surface area totals 2(5)=10. So then D, 6/10=3/5 is the surface area.

Is this clear?

Cheers!
J

I'm back

Kudos [?]: 759 [0], given: 355

Intern
Joined: 23 Dec 2014
Posts: 49

Kudos [?]: 11 [0], given: 53

Re: What is the ratio of the surface area of a cube to the surfa [#permalink]

### Show Tags

27 Jan 2015, 14:38
Assume the length is Y

Surface are of Cube= 6Y^2

As the length is doubled for rectangle , other remains same. That means, rectangle's width,and height is "Y" but it's length is "2Y" now.

Let's see the surface area of Rectangle

Length = 2Y
Width = Y
Height = Y

So,
Multiplying length with height, 2Y x Y = 2Y^2 . Since there are two sides then it will be multiplied by two. So it will be 4Y^2

Multiplying length with width, 2Yx Y = 2Y^2 .Now multiply with two and we get 4Y^2

Multiplying Width with height, Y x Y = Y^2 Now multiply with two and we get 2Y^2

After Adding them , 4Y^2+4Y^2+2Y^2 = 10Y^2

Now,
6y^2/10Y^2 = 3/5

Kudos [?]: 11 [0], given: 53

Veritas Prep GMAT Instructor
Joined: 16 Oct 2010
Posts: 7796

Kudos [?]: 18130 [0], given: 236

Location: Pune, India
Re: What is the ratio of the surface area of a cube to the surfa [#permalink]

### Show Tags

27 Jan 2015, 21:15
enigma123 wrote:
What is the ratio of the surface area of a cube to the surface area of a rectangular solid identical to the cube in all ways except that its length has been doubled?

A. 1/4
B. 3/8
C. 1/2
D. 3/5
E. 2

Another way to think about it:

Imagine the cube with 6 equal faces. The surface area will be 6s^2 (s is the length of the edge of the cube).
Now imagine pulling on one face of the cube to elongate it. Now you have 4 extra equal faces on the four sides. The extra surface area is 4s^2.

Ratio of surface area of cube:surface area of rectangular solid = 6:10 = 3:5

_________________

Karishma
Veritas Prep | GMAT Instructor
My Blog

Get started with Veritas Prep GMAT On Demand for $199 Veritas Prep Reviews Kudos [?]: 18130 [0], given: 236 Board of Directors Joined: 17 Jul 2014 Posts: 2698 Kudos [?]: 450 [0], given: 208 Location: United States (IL) Concentration: Finance, Economics GMAT 1: 650 Q49 V30 GPA: 3.92 WE: General Management (Transportation) Re: What is the ratio of the surface area of a cube to the surfa [#permalink] ### Show Tags 22 Nov 2015, 09:57 did it by knowing that surface area of a cube is always 6*side^2 since the rectangular has 2x as it's length and the rest is the same, we have: 2*(2x*x)+2(2x*x)+2x^2 = 10x^2 6x^2/10x^10 = 3/5 Kudos [?]: 450 [0], given: 208 EMPOWERgmat Instructor Status: GMAT Assassin/Co-Founder Affiliations: EMPOWERgmat Joined: 19 Dec 2014 Posts: 10391 Kudos [?]: 3690 [0], given: 173 Location: United States (CA) GMAT 1: 800 Q51 V49 GRE 1: 340 Q170 V170 Re: What is the ratio of the surface area of a cube to the surfa [#permalink] ### Show Tags 25 Nov 2015, 14:38 Hi All, This question can be solved by TESTing VALUES. You would likely find it helpful to physically draw the cube and solid. Since the answer choices do not include variables, we can use whatever values we'd like for the dimensions of the cube and for the rectangular solid (as long as we follow the Facts described in the prompt). Given the one specific rule (the length of the rectangular solid is double the length of the cube), I'll TEST the easiest VALUES that I can think of... Cube = (1)(1)(1) Solid = (1)(1)(2) Surface Area of Cube = 6(1) = 6 Surface Area of Solid = 2(1) + 4(2) = 10 Thus, the ratio of the two Surface Areas is 6:10 = 3:5 Final Answer: [Reveal] Spoiler: D GMAT assassins aren't born, they're made, Rich _________________ 760+: Learn What GMAT Assassins Do to Score at the Highest Levels Contact Rich at: Rich.C@empowergmat.com # Rich Cohen Co-Founder & GMAT Assassin Special Offer: Save$75 + GMAT Club Tests Free
Official GMAT Exam Packs + 70 Pt. Improvement Guarantee
www.empowergmat.com/

***********************Select EMPOWERgmat Courses now include ALL 6 Official GMAC CATs!***********************

Kudos [?]: 3690 [0], given: 173

Non-Human User
Joined: 09 Sep 2013
Posts: 14839

Kudos [?]: 287 [0], given: 0

Re: What is the ratio of the surface area of a cube to the surfa [#permalink]

### Show Tags

28 Feb 2017, 17:45
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________

Kudos [?]: 287 [0], given: 0

Re: What is the ratio of the surface area of a cube to the surfa   [#permalink] 28 Feb 2017, 17:45
Display posts from previous: Sort by