### The Math of Ex

Last year CBS canceled its TV series "The Ex-List" about an attractive girl who is searching for her future husband among her ex boyfriends, following the advice of a psychic. It may or may not be a bad fit with the Friday eve airing spot, but viewers were dropping on a weekly basis. Why would we, lovers of gossip and secrets; we, who smile remembering past romantic escapades; we, who enjoy secret revelations of our girlfriends' liaisons, turn away from watching something appetizingly named, “The Ex-List?” Is it possible that we prefer sweetly blurred memories and fantasies to the actual details of our, and others' past adventures, some which may have been embarrassing and naive?

There is an interesting, well-known mathematical paradox dealing with the number of sexual partners reported by heterosexual men and women. A number of different surveys, performed by respectful organizations, consistently report that men are claiming to have more partners than women. Depending on the country surveyed and specifics of the questions, the results vary but usually stay close to twice as many *reported* partners for heterosexual men than for women. But wait, read until the end before you start counting your exes.

A mathematical view of these results would suggest that this is impossible. If one adds up the number of heterosexual encounters women admitted to, it should equal the total of heterosexual encounters men claimed. Otherwise with whom would they have had these heterosexual encounters? Imagine an isolated island inhabited by 5 men and 5 women. After a year on the island, all women report having 1 heterosexual encounter each, and all men 2 each. It would be 1 x 5 = 5 total for women and 2 x 5 = 10 for men, but these numbers (5 and 10) should match.

This implies that either men enjoy exaggerating their sexual prowess, or women try to meticulously cover some of them, with the truth hidded somewhere in the middle. So, keep this in mind the next time you ask your husband or boyfriend about his past affairs. If the answer is shockingly high, feel free to give it a 25% discount.

Here is another captivating story from TheMathMom: To fight or not to fight (with the police...)