In recent days, I have written about the errors we make in simple arithmetic problems. Even multiplying by 10 is not easy for some people, especially when a decimal point is involved, as it is at gasoline pumps.

In one of my columns about arithmetic, I discussed a suggestion to save 16 million gallons of gasoline. I pointed out that when 16 million gallons are divided among 100 million vehicles, the benefit to each motorist is less than one-sixth of a gallon.

I added that one-sixth of a gallon is "about five fluid ounces, or half a glass of beer." Alvin Perloff of Silver Spring congratulated me on inserting an error of my own into that column as a subtle demonstration of how easy it is to make a mistake. He referred, of course, to the fact that one-sixth of a quart (not gallon) is about half a glass of beer. I had confused quarts and gallons.

District Liner Perloff is obviously a kind man. However, the truth is that my mistake was born of carelessness, not subtlety. Even in Cincinnati, where I was raised, nobody serves a short beer that contains one-sixth of a gallon. Mea culpa. For columnists, to err is not only human, it is usual.