[The following item appeared in the “From the File” section of The ARITHMETIC TEACHER, October 1983, p. 53. Later it was referenced in other NCTM publications.]
Here is a novel activity that can be used with selected dates—for example, March 27, 1981—which might be introduced to the class in the following way:
“Today is a special day for mathematicians. To see why, let’s write the date in the usual brief form, 3/27/81. Notice that we can also state this as a multiplication sentence, 3 × 27 = 81. Interesting, wouldn’t you say! Let’s call this a product date. Are there any more product dates in 1981?”
After students have had time to explore this question and find answers, the following questions can be posed:
1. Did last year have any product dates? If so, when?
2. Will next year have any product dates? If so, when?
3. Did your birthday fall on a product date?
4. How many product dates are there in any specific decade, say, the 1970s, the 1960s, and so on. List them.
5. The BIG question: How many product dates are there in a whole century? List them.
From the file of Terrel Trotter, Jr., McKinley Middle School, Harvey, IL 60426 (who found the idea in the Journal of Recreational Mathematics, April 1969 and October 1972)