A jar contains 20 marbles:4 red,6 white and 10 blue.If you remove one at a time,randomly,what is the minimum number that
问题描述：
A jar contains 20 marbles:4 red,6 white and 10 blue.If you remove one at a time,randomly,what is the minimum number that must be removed to be certain tat you have at least 2 marbles of each colors?
A) 6 B) 10 C) 12 D) 16 E) 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,
答
中文意思是 4 红,6白,10蓝,每次随机拿一个球,问最少需要拿多少个才能确定里边含有2红、2白、2蓝.我的思路是这样,考虑极端恶劣情况：前10个,均为蓝.已拿10个,完成2个蓝.再拿2个,均为白.已拿12个,完成2蓝,2白.再拿2个,...