One partner breaks his or her train into two parts, places one part in each hand, and places them on an index card. The second partner tries to break his or her train into two different parts. Partners continue building and breaking trains until all possible combinations have been made and are displayed on the index cards. Students should be able to justify why they think they have exhausted all possibilities. Challenge students to find other possibilities for a number by breaking its train into more than two parts.
Students work in pairs.
Partners take turns testing objects for attraction to the magnet. Students plan for arranging the two groups, those attracted and those not attracted, so that they can compare the two groups. Encourage students to make observations about the two groups. Listen for references to relative numbers of objects. Students continue to add to the collection.