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Splitting white and black balls into bowls of three

Question

There are 77 identical white balls and 88 identical black balls, and 55 distinguishable bowls. In how many ways can all the balls be placed so that every bowl ends up with exactly 33 balls?

Short answer

155155. Once each bowl's number of white balls is set, black balls fill the rest uniquely, so count w1+⋯+w5=7w_1+\dots+w_5=7 with 0≤wi≤30\le w_i\le3. Stars and bars gives (114)=330\binom{11}{4}=330; subtract the 5(74)=1755\binom74=175 solutions where some bowl has at least 4 (two such bowls is impossible), leaving 155155.

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