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# In how many ways 9 identical marbles can be placed in 3 identical boxes?

Since both the marbles and boxes are identical, the arrangement
order is not considered.
Only combinations of 3 numbers whose total is 9 are to be counted.
$(9,0,0),(8,1,0),(7,2,0),(7,1,1),(6,3,0),(6,2,1),$
$(5,4,0),(5,3,1),(5,2,2),(4,4,1),(4,3,2),(3,3,3)$
There are 12 such combinations.
$\therefore$ The required no. of ways = 12