ABSTRACT
He placed an acetate copy of the sheet on the overhead projector. He said, “I want you to turn the sheet so the large rectangle is at the top. You can see how I have set it up on the overhead projector. Th en I want you to write the numeral 1 in the middle of the largest rectangle. Sarah, after you do that on your sheet, please go up and write the numeral 1 on the overhead sheet (see second diagram on next page). Th is tells us that the bar is the unit that we will use for our work.” He continued to move around the room to help students who did not understand.
