everyone shakes hands with everyone else in a room . total number of handshakes is 55 . number of persons = ?
"in a room of n people , the number of possible handshakes is c ( n , 2 ) or n ( n - 1 ) / 2 so n ( n - 1 ) / 2 = 55 or n ( n - 1 ) = 110 or n = 11 answer is ( c )"
divide(divide(multiply(55, const_2), const_3), const_4)