Give each pair of students a piece of poster board and a set of glue sticks. Give one student in each pair a set of 10 2-inch strips of yellow paper and the other student a matching set of blue strips. Assign the students with yellow paper to work on inches and the students with blue paper to work on centimeters.
Tell the students that the yellow strips are each 2 inches long and the blue strips are slightly over 5 centimeters long. Tell the students that there are 12 inches and 30.5 centimeters in a foot.
Have one student sit on each side of her piece of poster board. Tell her to glue the measuring strips to the poster board so their edges are touching each other, making two sides of a ruler. Have her glue enough strips to make a foot.
Hand out subdivided rulers to each student. Have them measure out individual inches and centimeters using the rulers, and then have them subdivide the units further. Point out that one student must work from left to right while the other works from right to left.