Partners try to select the number of cubes needed to make the next step.
Students discuss the reasoning they used in making their estimates. Students try to estimate how many cubes it would take to make the entire staircase. Encourage them to explain their reasoning. Each partner builds a train of a certain number of linking cubes, e.g., 5. One partner breaks his or her train into two parts, places one part in each hand, and places them on an index card.