+270 In how many ways can you distribute $8$ indistinguishable balls among $2$ distinguishable boxes, if at least one of the boxes must be empty?
+1257
In how many ways can you distribute $8$ indistinguishable balls among
$2$ distinguishable boxes, if at least one of the boxes must be empty?
If one of the two boxes is to remain empty, and if all eight balls have to be used,
then you have to put all eight balls into the other box. Only two ways to do that.
Either put the balls in box A and leave box B empty, or vice versa.
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