Posted by donna on Thursday, April 22, 2010 at 10:56pm.
At a party, there were 105 handshakes. If each person shook hands exactly once with every other person, how many people were at the party?

math  Reiny, Thursday, April 22, 2010 at 11:00pm
for n people there will be C(n,2) handshakes
C(n,2) = 105
n!/(2!(n2)!) = 105
n(n1)/2 = 105
n^2  n  210 = 0
(n15(n+14) = 0
n = 15 or n=14, but n > 0
so there were 15 people

math  sakshi, Saturday, April 16, 2016 at 1:20pm
Good
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