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How many unique handshakes if each person in a group of 10 give handshakes out to each and every other individual. (a) 100 (b) 50 (c) 45 (d) 20 (e) 10

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6 Answers


true, or 9+8+7+...+2+1

Dex on


None of those answers are correct. The follow-up question should be are we assuming that each person is only using 1 hand? For example, if everyone is only giving handshakes left to left, or left to right or right to right or right to left? Granted left to right and right to left would be awkward.

SDL on


45. Imagine it as a polygon of side 10. Or draw out triangle, square, pentagon, and see the pattern yourself, if you don't know the algorithm.

Anonymous on


I don't know why the person above doesn't say that n(n-1)/2 where n is the number of people in the group the intuition is that every person in the group (n) has to shake every other persons hand (n-1) and then we only want to count each interaction once.

Anonymous on


Or just do: (10 Combination 2) = 10!/(2!8!) = 45

rhan on


n(n+1)/2 Where n =9 Answer: 45

Aram Yayloyan on

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