Sum of Multinomial Coefficients!

Algebra Level 3

Solve For the last two digits of the expression:- i = 1 24 j i = 2020 2020 ! i = i 24 j i ! \boxed{\sum_{\sum_{i=1}^{24} j_{i} =2020}\frac{2020!}{\prod_{i=i}^{24} j_{i} !}}


This is an ORIGINAL problem.


The answer is 76.

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1 solution

Sahil Goyat
Nov 28, 2019

Putting n=2020 , m=24 and all ai =1 in the multinomial theorem we get:

( i = 1 m a i ) n = i = 1 m j i = n n ! i = 1 m j i ! i = 1 m ( a i ) j i (\sum_{i=1}^m a_{i} )^{n}= \sum_{\sum_{i=1}^m j_{i} =n} \frac{n!}{\prod_{i=1}^m j_{i} !}\prod_{i=1}^m (a_{i})^{j_{i}}

( i = 1 24 1 ) 2020 = i = 1 24 j i = 2020 2020 ! i = 1 24 j i ! i = 1 24 ( 1 ) j i (\sum_{i=1}^{24} 1 )^{2020}= \sum_{\sum_{i=1}^{24} j_{i} =2020} \frac{2020!}{\prod_{i=1}^{24} j_{i} !}\prod_{i=1}^{24} (1)^{j_{i}}

2 4 2020 = i = 1 24 j i = 2020 2020 ! i = 1 24 j i ! × 1 24^{2020}= \sum_{\sum_{i=1}^{24} j_{i} =2020} \frac{2020!}{\prod_{i=1}^{24} j_{i} !} \times 1 and 2 4 e v e n 24^{even} has the last two digits as 76 which is the answer.

Hope you enjoyed the problem :)

Nice.......... solution

Razing Thunder - 12 months ago

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