A father and his 12-year-old son pass by the condom rack in a drug store, and the son asks, "Gee, Dad, what are those?"
The father, thinking it was time for his son to learn about such matters, explains in great detail about the use of condoms.
"Well, what are these packages of 3 for?" asks the son.
"Oh, those are for high-school students on weekends. One for Friday, one for Saturday and one for Sunday," answers the father.
"And what are these 6-packs for?"
"Oh, those are for college students. Two for Friday, two for Saturday and two for Sunday."
"And what are these 12-packs for?"
"Oh, those are for married men. One for January, one for February, one for March..."