Rubik's Cube Comb

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Fahim Shahriar
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Rubik's Cube Comb

Unread post by Fahim Shahriar » Sun Jan 27, 2013 10:32 pm

A $3 \times 3$ Rubik's cube has different colors on its each sides.
In how many different ways the cube can be arranged ?
Name: Fahim Shahriar Shakkhor
Notre Dame College

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nafistiham
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Re: Rubik's Cube Comb

Unread post by nafistiham » Mon Jan 28, 2013 9:41 am

see the permutations part.
\[\sum_{k=0}^{n-1}e^{\frac{2 \pi i k}{n}}=0\]
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Fahim Shahriar
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Re: Rubik's Cube Comb

Unread post by Fahim Shahriar » Mon Jan 28, 2013 12:48 pm

I'm saying what I did.

The centers are fixed. Excluding centers there 20 small cubes outside. 8 of them are in the corners and 12 in middles.

12 middles can be arranged in 12! ways and as each middles has two colors, permutation for middles = $12!\times 2$

8 corners can be arranged in 8! ways and each has 3 colors. (According to rules they should be arranged in $3!=6$ ways. But actually they can be in 3 ways. Do it practically.) So permutations of corners = $8!\times 3$

TOTAL = $12!\times 2\times 8!\times 3$
Last edited by Phlembac Adib Hasan on Mon Jan 28, 2013 3:01 pm, edited 1 time in total.
Reason: use \times instead of x(to show a $\times$)
Name: Fahim Shahriar Shakkhor
Notre Dame College

sakibtanvir
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Re: Rubik's Cube Comb

Unread post by sakibtanvir » Thu Jan 31, 2013 5:20 pm

How?? :o :o Shouldn't it be $12! \times 2^{12} \times 8! \times 3^{8} ???$
I don't know If I am right or wrong...For the corner pieces the approach should be as below:
"There are $8$ corner pieces,Each piece having $3$ colors.For our advantage,at first we assume that each corner piece is painted with a distinct color(Not with the combination of 3).The permutation will be $8!$.Now we consider their position at this time we assume the corner pieces painted with 3 colors(their original state!).Name the Pieces as below:$A,B,C,D,E,F,G,H$.Notice,$A$ can hold 3 positions,$B$ can hold 3 positions,.....,H can hold 3 positions.So the total number of arrangement for the corner pieces will be $8! \times 3^{8}$.I have spent those word just to clarify my idea.
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Fahim Shahriar
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Re: Rubik's Cube Comb

Unread post by Fahim Shahriar » Thu Jan 31, 2013 6:11 pm

@sakibtanvir. You're right. I did the permutation for only one piece and forgot to do for others. Thanks to correct me..

So finally we get
$12! \times 2^{12} \times 8! \times 3^{8}$
Name: Fahim Shahriar Shakkhor
Notre Dame College

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