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A classmate party, everyone shook hands with each other, a total of 46 times, asked a total of several people to participate
Remember the wrong question, CN 2 = 45, n = 10
Five good friends meet and shake hands with each other. Each two shake hands once. The number of shaking hands is
Ten times
Because of 1 and 2.3.4.5, four times
2 and 3.4.5, three times
3 and 4.5, twice
Four and five, once
4+3+2+1=10
Also, because every two people can only shake hands once, so 2 can't shake hands with 1, 3 can't shake hands with 1.2, 4 can't shake hands with 1.2.3, 5 can't shake hands with 1.2.3.4
How many times do five students shake hands with each other? 100 students? M students?
5 people, total: 5 × 4 △ 2 = 10 times
100 people, total: 100 × 99 △ 2 = 4950 times
M people, total: m (m-1) / 2 times
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