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At a secret meeting, everyone shakes hands exactly once with every other person present. Altogether there are forty-five handshakes. How many people attended the meeting?

Each person shakes hands with nine others and each handshake is shared by two people.

Comments


Guilherme

**** SPOILER ALERT

Combination of N people in pairs:

N! / (2! * (N-2)!) = 45

N * (N - 1) = 90

N = 0 or N = 10 which is the answer.


debashish ghatak

10


Vishal barot

Formula is n(n-1)/2 In the given problem n(n-1)/2=45 this gives n=9 or n=10

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Tags
mathematics combinatorics


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