**Lesson:** Towers of Ten

**Grade Level:** k-2

**Skills:** One-to-one correspondence, ways to make ten, subtraction, addition, and comparing numbers.

**Materials:**

Unifix cubes

**Procedure:**

1. Put random piles of unifix cubes on tables

2. Have each student build a tower of 10 cubes with the cubes they find on the table

3. Have students count the cubes in their towers of ten as they point to each cube in their tower

4. Ask students to compare the heights of the towers. They should see they are all the same height

5. Have students remove one cube from their tower of ten. Have students compare the height. What do they notice? Why?

6. Ask students how many cubes are in their original tower (9 cubes). Explain that they now have 2 towers. The second tower has the one cube that they took off their tower of ten. What happens when they add the number of cubes of the two towers (they get 10)

7. Ask students to remove another cube from the first tower and attach it to the second tower. How many cubes are in each tower now?

First tower = 8

Second tower = 2

What happens when they add the number of cubes in the two towers together (8 + 2 = 10)

8. Continue removing one cube at a time from the first tower and attaching it to the second tower. After each ‘subtraction’ students should compare the heights of the their two towers and see that when added, the sum of the cubes is always 10.

**Note:** When the two towers have 5 cubes each, students can see they are the same height and are the double numbers fact 5 + 5 = 10.