A cube of side 5cm is painted on all its side. If it is sliced into 1 : Problem Solving (PS)

trahul4

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A cube of side 5cm is painted on all its side. If it is sliced into 1 [#permalink]

09 Jul 2007, 07:26

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A cube of side 5cm is painted on all its side. If it is sliced into 1 cubic centimer cubes, how many 1 cubic centimeter cubes will have exactly one of their sides painted?

A. 9
B. 61
C. 98
D. 54
E. 64

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cano

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Re: 3-D Cube Question [#permalink]

01 Aug 2011, 09:16

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I think the quickest way is to imagine in your mind 1 side of the cube. Understand that the border cubes will have more than one side painted, so the ones with only one side are the ones in the middle, in this case 3x3=9. Then multiply that by 6 sides. If you will make a diagram, make only one side and then multiply by 6. Don't waste the little precious time that you have.
See the picture below to understand it better. The green squares have adjacent surfaces painted. Only the blue ones have 1 side only painted.

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5cm cube.jpg [ 3.96 KiB | Viewed 73292 times ]

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Bunuel

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Re: A cube of side 5cm is painted on all its side. If it is sliced into 1 [#permalink]

01 Sep 2014, 01:55

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trahul4 wrote:

A cube of side 5cm is painted on all its side. If it is sliced into 1 cubic centimer cubes, how many 1 cubic centimeter cubes will have exactly one of their sides painted?

A. 9
B. 61
C. 98
D. 54
E. 64

Look at the image below:

Little cubes with exactly one painted side will be those 3*3=9, which are in the center of each face. (6 faces)*(9 per each) = 54.

Answer: D.

Similar questions to practice:
the-entire-exterior-of-a-large-wooden-cube-is-painted-red-155955.html
a-big-cube-is-formed-by-rearranging-the-160-coloured-and-99424.html
64-small-identical-cubes-are-used-to-form-a-large-cube-151009.html
a-wooden-cube-whose-edge-length-is-10-inches-is-composed-of-162570.html
if-a-4-cm-cube-is-cut-into-1-cm-cubes-then-what-is-the-107843.html
a-large-cube-consists-of-125-identical-small-cubes-how-110256.html

3-D Geometry Questions to practice: 3-d-geometry-questions-171024.html
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wudy

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Joined: 07 Feb 2007

Posts: 121

Re: A cube of side 5cm is painted on all its side. If it is sliced into 1 [#permalink]

09 Jul 2007, 07:31

1

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trahul4 wrote:

A 5 cubic centimeter cube is painted on all its side. If it is sliced into 1 cubic centimer cubes, how many 1 cubic centimeter cubes will have exactly one of their sides painted?

A. 9
B. 61
C. 98
D. 54
E. 64

D. 6*9=54. A cube has 6 sides, each of which has 9 cubes with one sides painted.
32223
21112
21112
21112
32223

sumande

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Joined: 04 Jun 2007

Posts: 144

Re: A cube of side 5cm is painted on all its side. If it is sliced into 1 [#permalink]

09 Jul 2007, 07:33

1

Kudos

trahul4 wrote:

A 5 cubic centimeter cube is painted on all its side. If it is sliced into 1 cubic centimer cubes, how many 1 cubic centimeter cubes will have exactly one of their sides painted?

A. 9
B. 61
C. 98
D. 54
E. 64

9 such cubes for each of the 6 surfaces = 9 * 6 = 54 cubes. (D)

Andrey2010

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Joined: 05 Apr 2007

Posts: 7

Re: A cube of side 5cm is painted on all its side. If it is sliced into 1 [#permalink]

09 Jul 2007, 08:26

1

Kudos

Dear Wudy and Sumande

Please make the solution more clear.

First I don't understand how to get integer from 5 ^ 1/3 to get dimension of cube.

Also if you're talking about 9 cubes for every surface (3 x 3 x 3) and we're looknig for cubes with exactly one side painted that the solution is 6. One middle cube has only one painted side on every surface.
Or I didn't undertand the condition. Please explain.

Thank you in advance.

r019h

Manager

Joined: 04 Jun 2007

Posts: 149

Re: A cube of side 5cm is painted on all its side. If it is sliced into 1 [#permalink]

10 Jul 2007, 09:49

trahul4 wrote:

A 5 cubic centimeter cube is painted on all its side. If it is sliced into 1 cubic centimer cubes, how many 1 cubic centimeter cubes will have exactly one of their sides painted?

A. 9
B. 61
C. 98
D. 54
E. 64

are you sure it's a 5 cubic centimeter cube or is it a 5 cubic metre cube?? there should be five 1 cubic centimeter cubes when a 5 cubic centimeter cube is cut up

wudy

Manager

Joined: 07 Feb 2007

Posts: 121

Re: A cube of side 5cm is painted on all its side. If it is sliced into 1 [#permalink]

10 Jul 2007, 10:38

Andrey2010 wrote:

Dear Wudy and Sumande

Please make the solution more clear.

First I don't understand how to get integer from 5 ^ 1/3 to get dimension of cube.

Also if you're talking about 9 cubes for every surface (3 x 3 x 3) and we're looknig for cubes with exactly one side painted that the solution is 6. One middle cube has only one painted side on every surface.
Or I didn't undertand the condition. Please explain.

Thank you in advance.

Well. I though the cube is 5*5*5 centimeter, or the question does not make sense-- how a 5 cubic centimeter cube is divided into 1 cubic centimeter cube?

The number listed above is how many faces painted for each 1cm*1cm cube on a surface.
32223
21112
21112
21112
32223

sumande

Manager

Joined: 04 Jun 2007

Posts: 144

Re: A cube of side 5cm is painted on all its side. If it is sliced into 1 [#permalink]

10 Jul 2007, 10:46

wudy wrote:

Andrey2010 wrote:

Dear Wudy and Sumande

Please make the solution more clear.

First I don't understand how to get integer from 5 ^ 1/3 to get dimension of cube.

Also if you're talking about 9 cubes for every surface (3 x 3 x 3) and we're looknig for cubes with exactly one side painted that the solution is 6. One middle cube has only one painted side on every surface.
Or I didn't undertand the condition. Please explain.

Thank you in advance.

Well. I though the cube is 5*5*5 centimeter, or the question does not make sense-- how a 5 cubic centimeter cube is divided into 1 cubic centimeter cube?

The number listed above is how many faces painted for each 1cm*1cm cube on a surface.
32223
21112
21112
21112
32223

My assumption was exactly the same. I didn't think that a cube of side 5^(1/3) cm being divided into 1 cubic centimeter cubes makes sense. So, I assumed that each of the sides of the cube was 5 cm (a 5 cm cube as opposed to 5 cubic centimeter).

defenestrate

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Joined: 27 Jul 2006

Posts: 159

Re: A cube of side 5cm is painted on all its side. If it is sliced into 1 [#permalink]

10 Jul 2007, 22:19

2

Kudos

There is another way to do this problem. We know that all of the squares on each side have 2 sides (or 3 sides) painted. we want to remove them.

Make a new square which represents all of these squares. 5-2(one inch from each edge)=3

3.3=9 squares on each side.

9.6 sides is 54 squares

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A cube of side 5cm is painted on all of its sides. If it is [#permalink]

01 Aug 2011, 08:23

1

Kudos

A cube of side 5cm is painted on all of its sides. If it is sliced into 1 cubic cm cubes, how many 1 cubic cm cubes will have exactly one of their sides painted?

A. 9
B. 61
C. 98
D. 54
E. 64

Show Spoiler

D. This came straight from the GMAT club math review, but I'm a bit tripped up on the explanation

puneet478

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Joined: 14 Oct 2009

Posts: 45

Location: India

Re: 3-D Cube Question [#permalink]

01 Aug 2011, 08:30

2

Kudos

The answer is 'D'.

A 5 cm^3 cube divided in 1cm^3 cubes = 125 cubes in total. A cube has 6 faces.
On each face, all the cubes surrounding the boundary will have more than 1 side painted, which makes total of 5+5+3+3 = 16 cubes.

So we are left with 25-16 = 9 cubes on each face (which has only 1 side painted) totaling to 9*6=54 cubes.

Spidy001

Senior Manager

Joined: 01 Feb 2011

Posts: 309

Re: 3-D Cube Question [#permalink]

01 Aug 2011, 11:46

all the boundary cubes will have more than one face painted. only the center ones on each side of the larger cube, will have paint on just one side.

if we observer one face, there are 9 such cubes which have only one face painted.

so this times 6 faces we will have 9*6 = 54 such small cubes .

Answer is D.

gladvijay

Intern

Joined: 27 Feb 2011

Posts: 22

Re: 3-D Cube Question [#permalink]

01 Aug 2011, 13:50

the smaller cubes which will share an edge will have more than 2 faces painted.. so only the center cubes will have to be considered.. so .. 3*3 on each face.. 6 faces = 54

154238

Intern

Joined: 09 Sep 2012

Posts: 26

Location: United States

Re: 3-D Cube Question [#permalink]

23 Sep 2012, 03:04

puneet478 wrote:

The answer is 'D'.

A 5 cm^3 cube divided in 1cm^3 cubes = 125 cubes in total. A cube has 6 faces.
On each face, all the cubes surrounding the boundary will have more than 1 side painted, which makes total of 5+5+3+3 = 16 cubes.

So we are left with 25-16 = 9 cubes on each face (which has only 1 side painted) totaling to 9*6=54 cubes.

Hi.. is there any formula to calculate total number of cubes after division.
Let say a 6cm cube is divided into 2cm cubes ?

PareshGmat

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Re: A cube of side 5cm is painted on all of its sides. If it is [#permalink]

21 Feb 2013, 01:00

1

Kudos

Yes there is
it will be 6^3 / 2 ^3 = 27 cubes made

B

mau5

Verbal Forum Moderator

Joined: 10 Oct 2012

Posts: 485

Re: 3-D Cube Question [#permalink]

21 Feb 2013, 05:41

cano wrote:

I think the quickest way is to imagine in your mind 1 side of the cube. Understand that the border cubes will have more than one side painted, so the ones with only one side are the ones in the middle, in this case 3x3=9. Then multiply that by 6 sides. If you will make a diagram, make only one side and then multiply by 6. Don't waste the little precious time that you have.
See the picture below to understand it better. The green squares have adjacent surfaces painted. Only the blue ones have 1 side only painted.

For those who have a problem in visualising they can atleast come to a conlusion that such cubes will be present on all the six sides. Now, whatever be this number(9 in this case), the answer will be a multiple of 6. Thus, just choose an option which is a multiple of 6.
However, GMAT can give 2 options where in more than 1 option is a multiple of 6. In this question, luckily we have only one such option.

D.
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snehamd1309

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Joined: 29 Sep 2012

Posts: 7

A cube of side 5cm is painted on all its side. If it is sliced into 1 [#permalink]

10 Sep 2014, 21:14

Bunuel wrote:

trahul4 wrote:

A cube of side 5cm is painted on all its side. If it is sliced into 1 cubic centimer cubes, how many 1 cubic centimeter cubes will have exactly one of their sides painted?

A. 9
B. 61
C. 98
D. 54
E. 64

Look at the image below:

Little cubes with exactly one painted side will be those 3*3=9, which are in the center of each face. (6 faces)*(9 per each) = 54.

Answer: D.

Similar questions to practice:
the-entire-exterior-of-a-large-wooden-cube-is-painted-red-155955.html
a-big-cube-is-formed-by-rearranging-the-160-coloured-and-99424.html
64-small-identical-cubes-are-used-to-form-a-large-cube-151009.html
a-wooden-cube-whose-edge-length-is-10-inches-is-composed-of-162570.html
if-a-4-cm-cube-is-cut-into-1-cm-cubes-then-what-is-the-107843.html
a-large-cube-consists-of-125-identical-small-cubes-how-110256.html

3-D Geometry Questions to practice: 3-d-geometry-questions-171024.html

Hi Bunuel, When u show the image then i can quickly make out the answer and it gets very easy but this kind of 3-D accurate figure cant be drawn on paper and difficult to be thought in mind within 2 minutes. What should be done??

What is the best way to solve such questions?

PareshGmat

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Status:The Best Or Nothing

Posts: 1563

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Re: A cube of side 5cm is painted on all its side. If it is sliced into 1 [#permalink]

10 Sep 2014, 22:43

3

Kudos

snehamd1309 wrote:

Bunuel wrote:

trahul4 wrote:

A cube of side 5cm is painted on all its side. If it is sliced into 1 cubic centimer cubes, how many 1 cubic centimeter cubes will have exactly one of their sides painted?

A. 9
B. 61
C. 98
D. 54
E. 64

Look at the image below:
Little cubes with exactly one painted side will be those 3*3=9, which are in the center of each face. (6 faces)*(9 per each) = 54.

Answer: D.

Hi Bunuel, When u show the image then i can quickly make out the answer and it gets very easy but this kind of 3-D accurate figure cant be drawn on paper and difficult to be thought in mind within 2 minutes. What should be done??

What is the best way to solve such questions?

Not Bunuel, but lets try..

Refer diagram below; just imagine one side of the cube

Attachment:

cube.png [ 1010 Bytes | Viewed 71641 times ]

It will have 5 * 5 = 25 squares of 1 units

The border (the corner squares) will always be 2 side painted, so remaining are the pink shaded squares

There calculation per side = (5-2) * (5-2) = 3*3 = 9
(Two rows & two Columns are to be subtracted)

Total 6 sides = 9*6 = 54

Answer = 54

keyvan37

Intern

Joined: 08 Aug 2014

Posts: 1

Re: A cube of side 5cm is painted on all its side. If it is sliced into 1 [#permalink]

15 Sep 2014, 03:14

1

Kudos

Shouldn't it ask " A cube of side 5cm is painted on all its faces"

gmatclubot

Re: A cube of side 5cm is painted on all its side. If it is sliced into 1 [#permalink]

15 Sep 2014, 03:14

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A cube of side 5cm is painted on all its side. If it is sliced into 1

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