Math Activities For Addition and Subtraction: Montessori Addition Strip Board

Overview of The Board

The Montessori addition strip board consists of a large rectangular board with a grid of squares 12 high and 18 across. Above the squares are written the numerals from 1 to 18. Numerals 1 – 10 are written in red; numerals 11 – 18 are written in blue. The grid is blue, with a red line dividing it between 10 and 11.

Accompanying the board are blue and red strips, numbered 1 – 9. The solid blue strips measure as long as the red number printed on the right side. The red strips are marked off at each increment, with a blue numeral at the right side.

Purpose

The Montessori addition strip board is one method used by students to assist them in their abstract memorization of addition facts up to 18. While the materials are somewhat abstract, the process is still concrete.

Prior Learning Requirements

Children need to be familiar with the process of addition prior to using the addition strip board. The process in Montessori is taught through use of both the golden beads and the stamp game when teaching static and dynamic addition of quantities in the thousands.

Math Activities for Addition and Subtraction

1. Invite the child to a lesson on the addition strip board. To set up the board on the rug, place the board to the left. Line up the blue strips in increasing order, from 1 – 9, to the right of the board. Next, line up the red strips from 1 – 9, below the blue strips.
2. In the initial presentation with the addition strip board, children will learn how to add 1 and each number from 1 to 9.
3. Place the blue strip marked “1” in the first square on the board. Place the red strip that is marked “1” next to it. Say, “1 and 1 are 2”. Note that the two strips, when next to each other, will end beneath the numeral “2” on the board, as they cover two squares on the board. Write the equation 1 + 1 = 2 on the paper.
4. Return the red strip to the rug. Take the red strip marked “2” and place it next to the blue “1”. Explain how the strips equal 3 by counting the red strip, saying, “1 and 1, 2 make 3.” Write the equation 1 + 2 = 3.
5. Continue this process until all of the red strips have been counted with the “1” blue strip, writing each equation on the paper. Return the blue “1” to the right side of the board.
6. Now put the blue “2” strip on the board. Repeat the entire process with the red strips, this time starting counting at 2. (For example, with the blue 2 and the red 6 say, “2 and 1, 2, 3, 4, 5, 6 are 8.”)

Continue until all red strips have been added to each blue strip, documenting the equations along the way.

A Second Presentation Option

1. Invite the child to a second presentation with the addition strip board, called number analysis. Tell the child you are going to explore how many ways you can make the number 5.
2. Set up the strip board the same way as in the first lesson. Take the blue strip marked “6” and place it in the top row. Say, “6 and 0 make 6” and write the corresponding equation of 6 + 0 = 6.
3. Under this, place the blue strip marked “5” and the red strip marked “1”. Say, “5 and 1 make 6” and write the corresponding equation of 5 + 1 = 6.
4. Next place the blue strip marked “4” and the red strip marked “2”. Count the red strip, saying “4 and 1, 2 make 6.” Write the corresponding equation of 4 + 2 = 6. Continue until you reach the equation of 0 + 6 = 6.

Independent Follow-Up Work

• Have the child create a booklet, with one page dedicated to each fact family.
• Provide a booklet for the child to fill out, using the addition strip board.
• Leave out a basket of equations printed on slips for the child to explore.