Addition Strip Board

Direct aim. To find and write every addition combination of the numbers 1 to 9, and to begin memorizing them.

Indirect aims, the ones you will not see at once

A board ruled 12 squares down by 18 across, with the numbers 1 to 18 printed along the top.

Nine blue strips, solid, numbered 1 to 9 by length. Nine red strips, divided into squares, also 1 to 9. That's how Nienhuis describes its set.

A sheet of paper ruled for one table, such as 1 + 1 to 1 + 9, and a pencil.

Addition charts to check against, if you have them. The boards we found didn't include charts; the build below shows a simple one.

This board isn't in Montessori's books of 1912 to 1917. It turns her number-rod addition, two rods laid end to end, into strips the child can repeat many times.

1. 1Set the board on the table and lay the blue strips in a stair at its left, 1 to 9. Lay the red strips in a stair at its right.Say "I'm going to show you how to find some sums." Then nothing more.
2. 2Write the first fact on the sheet: 1 + 1.Say Read it as you write: "One plus one."
3. 3Place the blue 1 strip on the top row, at the left edge.Silent Line it up with the left edge carefully.
4. 4Place the red 1 strip right after it, touching end to end.Silent Ends touching, no gap.
5. 5Run a finger up from the end of the red strip to the number above, read it, and write 2 on the sheet.Say "Two." Then write it.
6. 6Take the red strip off and put the red 2 in its place for 1 + 2. Carry on to 1 + 9.Silent Change only the red strip. The blue one stays put.
7. 7Invite the child to do the next table, starting with the blue 2 strip.Say "Would you like to try the twos?" Then sit back.

The sum creeping one square to the right each time.

A sum that crosses past 10 into the teens.

Finding the same answer from 3 + 6 and 6 + 3.

A full sheet of one table, written by the child.

The strips and the chart. A gap between strips, or a strip off the left edge, puts the end under the wrong number, and the child can see it. A finished sheet is checked against an addition chart rather than by the adult.

Montessori’s name for this check is the control of error.

• Finding every way to make one sum, such as all the pairs that make 10
• Writing a whole table and checking it against a chart
• Facts with the strips swapped, blue for red, to see the sum stay the same
• Doubles: 1 + 1, 2 + 2, up to 9 + 9
• Later, the subtraction strip board and the addition snake game

Variations

This work needs only the material, so it has no printable of its own. The shelf plan below places it among the other works for the same age.

Free to print for your family, no email needed. Print at 100%, not “fit to page”, so the drawings keep their scale. Every printable on the site is listed on the printables page.

Ready for the first presentation

Ready for the next lesson

Short wooden strips are a choking risk for a toddler sibling. Count them back in.

We have not bought the paid homeschool curricula, so they are not listed here.

1. Maria Montessori, Dr. Montessori's Own Handbook (1914)

   Arithmetic

   Laying the shortest rods next to the longest, so that each pair is as long as the longest rod, represents the addition of numbers within ten: 9 + 1, 8 + 2, 7 + 3, 6 + 4.

   To add 8 to 2 the child places two rods next to one another, one with eight equal lengths and the other with two, instead of adding loose marbles one by one.

2. Maria Montessori, The Montessori Method (1912)

   Chapter XIX, Addition and Subtraction From One to Twenty

   The first exercise with the rods is to put the shorter pieces together to form tens, with commands such as take one and add it to nine, take two and add it to eight.

   Little by little the child is taught the technical language, nine plus one equals ten, and if he can write he is taught the signs plus and equals.

   Once the children have mastered this exercise they multiply it spontaneously, finding that three can be made in two ways and writing 2 + 1 = 3.

   Chapter XIII, Education of the Sense of Vision

   With the long rods divided into red and blue spaces one may count from one to ten and construct the addition and other tables.

3. Maria Montessori, The Montessori Elementary Material (1917)

   Part III, The Multiplication Table

   For the multiplication table the child fills printed sheets with his results, ten copies of each so he can repeat each exercise, and so learns the multiplications by memory.

Lesson text and the scope and sequence are CC BY 4.0: reuse them with credit to Owen Wren, Homeschool Montessori, and a link. Photos and illustrations are all rights reserved. Terms.