Boys and girls! The pill costs $XXX, condoms $YYY. Sheila uses both and spends $ZZZ. How many times a day is she getting laid?
Gosh, this is supposed to be a family friendly site. But unfortunately this topic has gotten thrust way out into the open, no dirty allusion intended.
I performed this calculation when John Holmes died, based on his own claims. He averaged 3.5/day.