Innumeracy, sort of

Recently, this NYT article made the rounds. It is about the implications of the fact that in most large American colleges, the ratio of female to male students is approaching 6/4. In the article, we read the following:

Jayne Dallas, a senior studying advertising who was seated across the table, grumbled that the population of male undergraduates when you looked at it as a dating pool. "Out of that 40 percent, there are maybe 20 percent that we would consider, and out of those 20, 10 have girlfriends, so all the girls are fighting over that other 10 percent," she said.

Now it's fairly clear what Jayne Dallas is trying to say. What she actually means is "Out of that 40 percent, there is maybe 50 percent that we would consider, 50 percent of those have girlfriends, so all the girls are fighting over that other 10 percent." But even though we know what she means, the quote still should have been edited, because she uses her terminology incorrectly; 20 percent out of 40 percent is 8 percent, not 20, and 10 percent out of 20 percent is 2 percent, not 10.