GMAT Question of the Day - Daily to your Mailbox; hard ones only

It is currently 06 Dec 2019, 20:36

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

A cube of side 7 cm is coloured on pair of opposite faces by

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:

Hide Tags

Find Similar Topics 
Manager
Manager
User avatar
Joined: 25 Sep 2012
Posts: 228
Location: India
Concentration: Strategy, Marketing
GMAT 1: 660 Q49 V31
GMAT 2: 680 Q48 V34
GMAT ToolKit User Reviews Badge
A cube of side 7 cm is coloured on pair of opposite faces by  [#permalink]

Show Tags

New post 04 Nov 2013, 22:31
1
13
00:00
A
B
C
D
E

Difficulty:

  65% (hard)

Question Stats:

61% (02:19) correct 39% (02:20) wrong based on 264 sessions

HideShow timer Statistics

A cube of side 7 cm is coloured on pair of opposite faces by Red, Green and Yellow shades. The cube is then cut into unit cubes. How many of the unit cubes will have exactly two coloured faces?

A) 150
B) 125
C) 60
D) 49
E) 40
Most Helpful Expert Reply
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 59587
Re: A cube of side 7 cm is coloured on pair of opposite faces by  [#permalink]

Show Tags

New post 05 Nov 2013, 00:45
5
2
b2bt wrote:
A cube of side 7 cm is coloured on pair of opposite faces by Red, Green and Yellow shades. The cube is then cut into unit cubes. How many of the unit cubes will have exactly two coloured faces?

A) 150
B) 125
C) 60
D) 49
E) 40


Look at the figure below:
Attachment:
Untitled.png
Untitled.png [ 67.67 KiB | Viewed 5105 times ]
Only the edge cubes marked with dots will have exactly two colored faces. 5 cubes per edge * 12 edges = 60 cubes.

Answer: C.

Hope it's clear.

P.S. A cube has 12 edges. There are 4 edges on the top square, 4 on the bottom square and 4 more that connect the 2 squares.
_________________
Most Helpful Community Reply
Intern
Intern
avatar
B
Joined: 24 Jul 2017
Posts: 43
Location: India
WE: Information Technology (Computer Software)
Re: A cube of side 7 cm is coloured on pair of opposite faces by  [#permalink]

Show Tags

New post 09 Sep 2017, 07:47
5
3
Perfectly explained by Bunuel.
Just wanted to add few more points to solve such questions quickly.

Below are the formulae that can be used to find different number of cubes colored:
For a cube:
Number of cubes with 0 side painted= (n-2) ^3
Number of cubes with 1 sides painted =6(n - 2) ^2
Number of cubes with 2 sides painted= 12(n-2)
Number of cubes with 3 sidess painted= 8(always)

Thanks
General Discussion
Intern
Intern
avatar
B
Joined: 09 Oct 2017
Posts: 14
Location: Viet Nam
GMAT 1: 530 Q35 V28
GPA: 3.1
GMAT ToolKit User
A cube of side 7 cm is coloured on pair of opposite faces by  [#permalink]

Show Tags

New post 30 Sep 2019, 19:51
devanshu92 wrote:
Perfectly explained by Bunuel.
Just wanted to add few more points to solve such questions quickly.

Below are the formulae that can be used to find different number of cubes colored:
For a cube:
Number of cubes with 0 side painted= (n-2) ^3
Number of cubes with 1 sides painted =6(n - 2) ^2
Number of cubes with 2 sides painted= 12(n-2)
Number of cubes with 3 sidess painted= 8(always)

Thanks


Hi devanshu92 and bunuel, can you please elaborate more on the above formula? What does n stand for? Is that n= length of side?
Intern
Intern
avatar
B
Joined: 13 May 2018
Posts: 19
Re: A cube of side 7 cm is coloured on pair of opposite faces by  [#permalink]

Show Tags

New post 22 Nov 2019, 16:37
hanvd1990 wrote:
devanshu92 wrote:
Perfectly explained by Bunuel.
Just wanted to add few more points to solve such questions quickly.

Below are the formulae that can be used to find different number of cubes colored:
For a cube:
Number of cubes with 0 side painted= (n-2) ^3
Number of cubes with 1 sides painted =6(n - 2) ^2
Number of cubes with 2 sides painted= 12(n-2)
Number of cubes with 3 sidess painted= 8(always)

Thanks


Hi devanshu92 and bunuel, can you please elaborate more on the above formula? What does n stand for? Is that n= length of side?

hanvd1990 nstands for the number of cubes formed . In this case the side is 7 and the cube is cut into unit cubes hence n=7
_________________
SACHIN SHARMA
努力の精神を養うこと (Fostering the spirit of Effort)
GMAT Club Bot
Re: A cube of side 7 cm is coloured on pair of opposite faces by   [#permalink] 22 Nov 2019, 16:37
Display posts from previous: Sort by

A cube of side 7 cm is coloured on pair of opposite faces by

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  





Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne