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Mythematics: a decimal point

Q: Just thought I’d let you know why the young lady in your Sept. 28, 2008, post lost the multiplication bee. When you’re speaking or writing numbers, the word “and” is actually the decimal point. So one hundred thirty-two is 132, but one hundred and thirty-two is 100.32. It may seems a small matter, but it makes a big difference in the number.

A: This is a common misconception, but in spoken or written numbers the conjunction “and” does not mean decimal point. So someone who says, “Twelve times eleven is one hundred and thirty-two” means the result is 132, not 100.32.

The number 132 can correctly be spoken or written as “one hundred thirty-two” or “one hundred and thirty-two.” British speakers and most Americans use “and,” but the conjunction is sometimes omitted in North American usage.

The “and” merely means “plus” and indicates that more of the number is coming. What follows “and” can be a whole number or a fraction, whether decimal or not (as in “three and five-eighths”).

Normally, someone speaking a decimal number like 100.32 would say “one hundred point thirty-two” or “one hundred point three two” or “one hundred and thirty-two hundredths.” When you use “and” in speaking a decimal number, the size of the decimal fraction (“tenths,” “hundredths,” and so on) must be included.

Our posting mentioned a child who lost a multiplication bee because she answered that 12 times 11 was “one hundred and thirty-two.” The correct answer, according to the contest sponsors, was “one hundred thirty-two,” so she was penalized for using “and.”

Apparently there was a special rule in the math contest against using “and” in answers. Contest rules are a kingdom unto themselves, and it may be that the usual practice in multiplication bees is to forbid the use of “and.”

But we can assure you that “and” does not mean “decimal point.” That is not among the definitions of “and” in any dictionary that we can find, and that includes standard dictionaries, the Oxford English Dictionary, and mathematical dictionaries.

As we said in our earlier posting, the OED’s entry for “and” lists this as one of its definitions: “to connect (units or) tens to hundreds (or thousands), as two hundred and one, three thousand and twenty-one, six thousand two hundred and fifty-six.”

In English, the earliest written references for this use of “and” are from the Lindisfarne Gospels, which were written in Old English in the late 7th or early 8th century. And the usage has been common practice ever since. We’re talking about more than 1,200 years of history.

The OED further explains that the “and” in numbers “is frequently omitted colloquially in North American usage.” This implies that including “and” is the more standard usage, while omitting it is an informal or conversational usage.

The use of “and” in numbers is a very ancient practice. You’re probably familiar with the now old-fashioned use, for example, of “one and twenty” to mean twenty-one, a convention that English inherited from the older Germanic languages.

“With numerals of the type one and twenty,” the OED says, “compare this type of composition in other Germanic languages, e.g. Old High German fiarzug inti sehso forty-six, Middle High German einz und drizic thirty-one, German einundzwanzig twenty-one, Old Icelandic einn ok tuttugu (also tuttugu ok einn ) twenty-one, etc.”

We don’t know where the misconception that “and” means “decimal point” came from. But unfortunately, it’s all over the Internet and apparently elementary-school teachers are even passing it on to their students. Never mind. It’s nonsense.

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