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一、“互相握手”型问题的计数方法原型某同学举行生日宴会,一共有20位同学参加.假设每两个同学互相握一次手,问:(1)每个同学握多少次手?(2)总共握手次数有多少?解析(1)每个同学与另外19个同学分
First, the “mutual handshake ” type of problem counting method A certain classmates hold a birthday party, a total of 20 students to participate in. Suppose every two students hold each other hands and ask: (1) how many times each classmate hands? (2) What is the total number of handshakes? Analysis (1) Each classmate and another 19 classmates