As part of an assessment, students tell how they would solve a particular problem and why. Understand and use relationships among operations and properties of operations. Students make up humorous stories about adding and subtracting zero. I had 27 cookies. My mean brother took away zero.
Discussions follow which lead to intuitive understandings of commutativity.
References Butler, M. Christina. Too Many Eggs. David R. Godine Publisher, 1988. G. P. Putnam's Sons, 1984. Take Away Monsters.