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What is the ratio of the surface area of a cube to the surfa [#permalink]
12 Feb 2012, 20:33

00:00

A

B

C

D

E

Difficulty:

35% (medium)

Question Stats:

63% (01:00) correct
36% (00:51) wrong based on 122 sessions

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?

Re: What is the ratio of the surface area of a cube to the [#permalink]
13 Feb 2012, 05:25

3

This post received KUDOS

Expert's post

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;

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

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

Answer: D.

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

Re: What is the ratio of the surface area of a cube to the [#permalink]
22 Jun 2013, 02:31

Expert's post

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.

Answer: D.

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.
_________________

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

D is the correct answer

Is this clear?

Cheers! J

I'm back

gmatclubot

Re: What is the ratio of the surface area of a cube to the surfa
[#permalink]
31 Mar 2014, 07:35