현재 위치 - 대출자문플랫폼 - QA안내 - There are 10 children playing a handshake game. Every two children can only shake hands once. How many times did they shake hands?

There are 10 children playing a handshake game. Every two children can only shake hands once. How many times did they shake hands?

9+8+7+6+5+4+3+2+ 1=45{ times} ....

Very simple ...

Because the first child can't shake hands with himself, he can only shake hands with nine other people.

Shake hands with 1 for the second time ... the remaining eight people shook hands. ..

The third one shakes hands with 1 and the second one, and the remaining seven shake hands. ..

etc ..

Equal to 45 times! ! —。 .—!

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