My mother once taught in a small country three-room schoolhouse, where students of different age levels often had to study the same course together. For the course in American History, the kids in the 6th, 7th, and 8th grades were combined into one class. This means that their ages were between 10 and 14. If [...]
Here is a famous old multiplication idea. Look at the two simple problems below. 51 21 × 3 × 6 153 126 The strange property here is that the digits that were used in the factors are the only ones that appear in the product! And even stranger is the fact that try as hard [...]
Part I Carefully find the products of these multiplication exercises. (A) 41 × 3 (B) 576 × 6 (C) 11728 × 2 Did you notice something interesting about your answers? If you did your work correctly, you should have noticed that the digits in each product were “in order”. That is rather interesting, don’t you [...]
Naming numbers according to some property or characteristic that they possess is a legitimate — albeit egotistic — activity of some mathematicians. (See Keith Numbers for a simple and elegant example.) Another interesting name category that I have recently learned about is called “Niven Numbers”. These are merely numbers that are divisible by the sum [...]
[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 [...]