Problem: everyone shakes hands with everyone else in a room . total number of handshakes is 91 . number of persons = ?
Rationale: "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 = 91 or n ( n - 1 ) = 182 or n = 14 answer is ( a )"
annotated_formula: divide(divide(multiply(91, const_2), const_3), const_4)