Discrete chocolates!

In how many ways can 12 different chocolates be equally divided among 3 children?


The answer is 34650.

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1 solution

Ashish Menon
Jul 23, 2016

Generalizing, lets calculate the nymber of ways in which n n chocolates can be equally distributed among n n children.
So, each child should get m n \dfrac{m}{n} chocolates.

First child can get chocolates in m C m n ^mC_{\frac{m}{n}} different ways. The The second child can get chocolates in m m n C m n ^{m-\frac{m}{n}}C_{\frac{m}{n}} different ways.
The third child can get chocolates in m 2 m n C m n ^{m-2\frac{m}{n}}C_{\frac{m}{n}} different ways.
The fourth child can get chocolates in m 3 m n C m n ^{m-3\frac{m}{n}}C_{\frac{m}{n}} different ways.
\large \vdots
The ( n 1 ) t h {(n-1)}^{th} child can get chocolates in m ( n 2 ) m n C m n ^{m-(n-2)\frac{m}{n}}C_{\frac{m}{n}} different ways.
The n t h n^{th} child can get chocolates in m ( n 1 ) m n C m n ^{m-(n-1)\frac{m}{n}}C_{\frac{m}{n}} different ways.

So, the total number of ways in which the chocolates can be equally distributed
= m C m n × m m n C m n × m 2 m n C m n × × m ( n 2 ) m n C m n × m ( n 1 ) m n C m n = m ! ( m n ) ! × ( m m n ) ! × ( m m n ) ! ( m n ) ! × ( m 2 m n ) ! × ( m 2 m n ) ! ( m n ) ! × ( m 3 m n ) ! × × ( m ( n 2 ) m n ) ! ( m n ) ! × ( m ( n 1 ) m n ) ! × ( m ( n 1 ) m n ) ! ( m n ) ! × ( m n m n ) ! = m ! ( m n ) ! n ^mC_{\frac{m}{n}} × ^{m-\frac{m}{n}}C_{\frac{m}{n}} × ^{m-2\frac{m}{n}}C_{\frac{m}{n}} × \cdots × ^{m-(n-2)\frac{m}{n}}C_{\frac{m}{n}} × ^{m-(n-1)\frac{m}{n}}C_{\frac{m}{n}}\\ \\ = \dfrac{m!}{\left(\frac{m}{n}\right)! × \left(m - \frac{m}{n}\right)!} × \dfrac{\left(m - \frac{m}{n}\right)!}{\left(\frac{m}{n}\right)! × \left(m - 2\frac{m}{n}\right)! }× \dfrac{\left(m - \frac{2m}{n}\right)!}{\left(\frac{m}{n}\right)! × \left(m - \frac{3m}{n}\right)!} × \cdots × \dfrac{\left(m - (n-2)\frac{m}{n}\right)!}{\left(\frac{m}{n}\right)! × \left(m - (n-1)\frac{m}{n}\right)!} × \dfrac{\left(m - (n-1)\frac{m}{n}\right)!}{\left(\frac{m}{n}\right)! × \left(m - n\frac{m}{n}\right)!}\\ \\ = \color{#20A900}{\boxed{\dfrac{m!}{{\left(\frac{m}{n}\right)!}^n}}}

So, plugging in m = 12 m = 12 and n = 3 n= 3 , we get, the number of ways of distributing the chocolates as:-
12 ! ( 12 3 ) 3 = 12 ! ( 4 ! ) 3 = 34650 \dfrac{12!}{{\left(\frac{12}{3}\right)}^3}\\ \\ = \dfrac{12!}{{\left(4!\right)}^3}\\ \\ = \color{#3D99F6}{\boxed{34650}}

Can we do it like this ?

The 1 st 1^{\text{st}} child can take any 4 4 chocolates from 12 12 : 12 C 4 ^{12}C_4

The 2 nd 2^{\text{nd}} child can take any 4 4 chocolates from 8 8 : 8 C 4 ^{8}C_4

The 3 rd 3^{\text{rd}} child can take any 4 4 chocolates from 4 4 : 4 C 4 ^{4}C_4

Total Possibilities : 12 C 4 × 8 C 4 × 4 C 4 = 34650 ^{12}C_4 \times ^{8}C_4 \times ^{4}C_4 = 34650

Sabhrant Sachan - 4 years, 10 months ago

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the perfect method i would say. ashish showed a bit rigorous generalisation

Satyabrata Dash - 4 years, 10 months ago

Ofcourse that is exactly how I have generalized!

Ashish Menon - 4 years, 10 months ago

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For some reason your proof looks confusing :/

Sabhrant Sachan - 4 years, 10 months ago

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@Sabhrant Sachan Oh I am sorry for that :( I will try to make it better.

Ashish Menon - 4 years, 10 months ago

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