摘要：九年级1班将竞选出正.副班长各1名.现有甲.乙两位男生和丙.丁两位女生参加竞选． (1)男生当选班长的概率是 , (2)请用列表或画树状图的方法求出两位女生同时当选正.副班长的概率． 解:(1),······································································································· 4分 (2)树状图为, ······························································································································ 8分 所以.两位女生同时当选正.副班长的概率是．· ·············································································································· 10分

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