Ajarcontains20marbles:4red,6whiteand10blue.Ifyouremoveoneatatime,randomly,whatistheminimumnumberthatmustberemovedtobecertaintatyouhaveatleast2marblesofeachcolors?
A)6B)10C)12D)16E)18
想问下答案是怎么算出来的,如果加减呢?我尝试用概率可是不知道怎么理解,