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【简答题】
一个口袋中装有标号为1，2，3的6个小球，其中标号1的小球有1个，标号2的小球有2个，标号3的小球有3个，现在口袋中随机摸出2个小球． （Ⅰ）求摸出2个小球标号之和为3的概率； （Ⅱ）求摸出2个小球标号之和为偶数的概率； （Ⅲ）用X表示摸出2个小球的标号之和，写出X的分布列，并求X的数学期望E（X）．
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