As a self described lesson collector, author Charles Lovett enjoys gathering "interesting" lessons and teasing them apart to find out what makes them "tick", particularly the pedagogy. He often wonders what decisions the teacher made that generated such an interesting and successful learning environment. Here he describes a…

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…

An activity providing practice with whole number addition and subtraction, as well as enlarging on the idea of numeration systems, is described. (DT)

A method of using a modified number line to illustrate concepts of addition, subtraction, multiplication, and division in a modular system is presented. (DT)

Reviewing addition through the use of palindromes is discussed. A rule for converting any number into a palindrome is presented. (MP)

A distinction is made between an algorithm and the justification for the algorithm. Examples of both are given for the operations with whole numbers. (DT)

An approach close to the original Greek geometric point of view regarding the question and proof of the irrationality of the square root of two is given. (MN)