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October 21, 2014

October 21, 2014

Posted by **Sam** on Monday, October 26, 2009 at 4:40pm.

- math -
**Reiny**, Monday, October 26, 2009 at 4:48pmLet the number of teachers be n

the number of handshakes of n people is

C(n,2)

so C(n,2) = 171

n!/(2!(n-2)!) = 171

n(n-1) = 342

n^2 - n - 342) = 0

(n-19)(n+18) = 0

n = 19 or n= -18, but n > 0

So 19 teachers came

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