These proceedings are a written record of the research presented at the 42nd annual meeting of the North American Chapter of the International Group for the Psychology of Mathematics Education (PME-NA) held in Mazatlán, Mexico, virtually beginning May 27, 2021 and in-person June 2-6, 2021. The conference was originally scheduled to take place…

The minimum number and type of whole-unit weights needed to balance any object is extended to the situation where weights may be placed on both pans of a balance scale. (DT)

Some techniques are given for relating the English system of liquid measure to base two numeration. (DT)

The nature and purposes of secondary school mathematics are discussed, with specific analysis of the role of algebra. Appropriate topics are suggested, with elaboration on level of abstraction and usefulness. (DT)

Activities are suggested for setting up a mathematics center for a week or more at a time. The activities relate to weight, counting, puzzles, length, graphing, and ordering. (MP)

Games and activities, which are fun, practical, and related to the child's world, are presented. Suggestions are given for building skills in estimating lengths, guessing how many, recognizing patterns in counting, multiplying with "waffles," classifying by attributes, and adding and subtracting with special cards, relays, and play…

This discussion of the mathematical potential of classroom events gives many examples of incidents that can be used for learning about topics such as one-to-one correspondence, counting, sets, ordering, time, fractions, money, shape, estimation, measuring, volume, area, number operations, and graphs. (MP)

This is part two of a two-part SMSG elementary school text for fourth-grade students. The content is aimed at the development of some of the fundamental concepts of mathematics such as number, numeration, the operations of arithmetic, and intuitive geometry. Chapter topics include properties and techniques of addition and subtraction, techniques…

The teacher's guide for Unit 8 of this SMSG series covers the two chapters on the real number system and on area, volume, and computation. The overall purpose for each of the chapters is described, the prerequisite knowledge needed by students is specified, the mathematical development of each chapter is detailed, behavioral objectives are stated,…

Several problems are identified: place values, time, even numbers, fractional parts, and temperature. Specific teaching suggestions are discussed. (MP)