I bring you the High School Prom Theorem:
We suppose that on the day after the prom, each girl is asked to give the number of boys she danced with. These numbers are then added up giving a number G. The same information is then obtained from the boys, giving a number B.One of the things it shows is that when, in surveys, men report having many more sexual partners than women, something is amiss. (Via.)
Proof: Both G and B are equal to C, the number of couples who danced together at the prom. Q.E.D.