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help me

by sana.noor » Fri Oct 25, 2013 9:41 am
You have a six-sided cube and six cans of paint, each a different color. You may not mix colors of paint. How many distinct ways can you paint the cube using a different color for each side? (If you can reorient a cube to look like another cube, then the two cubes are not distinct.)
(A) 24
(B) 30
(C) 48
(D) 60
(E) 120

OA:B
we can choose top of the cube in 6 ways. lets fix this point and then we can choose 5 different colors for the bottom B. as A is fix so we have 5 ways to choose bottom. the other 4 faces are in circular way and thus we have (1/4) (4!) = 6 ways to color it. in total we can color the cube in 5.6 = 30 ways.

this question is easy to do but my concern is what if we change the condition from non-distinct to distinct cubes??? what will be the answer then?
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by Mike@Magoosh » Fri Oct 25, 2013 10:34 am
sana.noor wrote:my concern is what if we change the condition from non-distinct to distinct cubes??? what will be the answer then?
Dear sana.noor,
I'm confused by your question. The problem specifies "distinct" cubes. Do you mean, changing the condition from distinct to non-distinct? If we want to count the number of non-distinct cubes, wouldn't that be infinite? We could paint a billion cubes exactly the same way, and they would be non-distinct. I would like to help you, but I am not sure what question you are asking.
Mike :-)
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by sana.noor » Fri Oct 25, 2013 7:52 pm
my question was if we take two cubes and we have 6 paints than how many distinct ways we can paint those two cubes (the two cubes should be distinct).
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by Mike@Magoosh » Sat Oct 26, 2013 12:12 pm
sana.noor wrote:my question was if we take two cubes and we have 6 paints than how many distinct ways we can paint those two cubes (the two cubes should be distinct).
Dear sana.noor
Well, if there are two cube, and each one can be painted in one of 30 ways, than we have 30 choices for the first cube, and then the second cube could have any pattern except the pattern on the first cube, so there would be 29 choices for the second cube.
30*29 = 870

Here, I used the Fundamental Counting Principle, which is discussed in this post:
https://magoosh.com/gmat/2012/gmat-quant-how-to-count/

Does this make sense?
Mike :-)
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by sana.noor » Sat Oct 26, 2013 7:50 pm
superb! thankyou
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