5 balls of different colours are to be placed in 3 boxes of different sizes. Each box can hold all 5 balls. Then in how many different ways can we place the balls so that none of the box remains empty? If the answer is N , find the value of 3 0 N + 4 !
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I disagree with multiplying by 3 ! , because there are only 3 distinct ways to arrange (3, 1, 1). The only choice is for which box to contain 3 balls, and there is only 1 way to do this.
hence, the answer should be 3 0 1 5 0 + 4 ! = 2 9 .
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No, all the boxes are of different size then how can you say that there is only 3 ways to arrange them? Each time you keep 3 balls in a box, there are 2 possibilities for other two. So total is 3 x 2 i.e. 3!
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Let's call the boxes Red, Blue and Green. We can choose to either have 3 balls in Red, 1 each in Blue and Green, or we can choose to have 3 balls in Blue, 1 each in Green and Red, or we can choose to have 3 balls in Green, 1 each in Red and Blue. This gives us 3 ways. If you say that there are 6 ways, please state the other 3.
The objections to your argument pointed out that the maximium possible number of permutations (without any restictions) is 3 5 = 2 4 3 . How can there be 3 0 0 > 2 4 3 such ordering?
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@Calvin Lin – Oh yes! Now I got what mistake I was doing. Sorry for inconvinience caused to you!
Typo: ( 3 5 ) ( 1 ∗ 2 ∗ ) ( 1 1 )
btw nice solution. ^__^
Aargh! I got tricked! I put down 150 and then gave up! -_-
Use the Stirling numbers of the second kind sequence where S(k,n) n! where k is number of balls and n number of boxes. In this case, S(5,3)=25 3!=150 ways. Since the answer is N/30 + 4!, answer is 29
Let's give boxes a name, A B and C.
First case: (3,1,1)
This case will have ( 3 5 ) ( 1 2 ) ( 1 1 ) ( 2 3 ) = 6 0 ways.
Second case: (2,2,1)
This case will have ( 2 5 ) ( 2 3 ) ( 1 1 ) ( 2 3 ) = 9 0 ways.
Therefore, there're total of 6 0 + 9 0 = 1 5 0 ways to do that.
Answer: 2 9 . :3
wow! you solution is great.
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Since, none of the box can't be kept empty, there are only two possibilties in which we can distribute the balls in 3 boxes. It is (3,1,1) or (2,2,1). And as the boxes and balls are of different size and colour respectively, we can arrange them among themselves in 3 ways. So total number of ways is, ( ( 3 5 ) ( 1 3 ) ( 1 1 ) + ( 2 5 ) ( 2 3 ) ( 1 1 ) ) 3 = 1 5 0 Hence, N = 150 so answer is, 3 0 1 5 0 + 4 ! = 2 9