Addition Strip Board

Materials:

Purposes:

To memorize the essential combinations and to see that no essential combination exists beyond 9 + 9.
To experience the commutative aspect of addition.

Age: 4 ½ - 5 ½

Preparation:

Presentation 1: Building the Essential Combinations

Invite the child for the lesson, to bring the board to a table, and the guide will bring the tray and the strips.
Draw attention to the numbers at the top and the red line.
Remove the blue strips and order them on the top left edge of the table 9-1.
Remove the red strips and organize the same way on the left edge of the table 9-1.
Open book to Table of 1.
Explain that the strips are used to find the answers but there are two rules:
- Always use two strips one blue and one red
- The blue strip is always first
Read the first problem to the child. Place blue 1 in the box under 1 and red strip 1 beside it.
Show the child the answer is above the end of the last strip.
Show the child how to write the answer.
Replace the strips.
Next problem: child reads the equation, places the strips, reads the strips, and writes the answer.
Now the blue 1 can stay on the board.
When the child has gone as far as they want to, show them how to check with Chart I.
Have the child bring Chart I to the table.
Have the child read aloud the first equation in the book and then from the chart to see if they match. Repeat for the rest. If there is an error, line through it and write the correct answer.
Show the child how to put them away in the box. Stand the box on its side and place strips in Longest to shortest in one color and then fill in the spaces in the other color.

Note: When the child sees the pattern in the answers and “runs” the numbers rather than using the strips, move to the next presentation.

Control of Error: Addition Control Chart 1

Presentation 2: How Many Ways to Make a Sum

The strips and board are set up as before.
Offer the child a number to select from 6-12. Example: 7
Explain you will find out how many ways to make 7.
Get the child a booklet.
Remind of the 2 rules.
Place blue 1 strip under the 1 on the board. And ask how many more are needed to make 7.
Count the squares up to 7 and find the red strip to match and place.
Place blue 2 strip below the blue 1. The child will count up to find which red strip they need and place it.
When the child is complete finding all the ways to make the number, the child will use Chart I to check.

Control of Error: Addition Chart I

Presentation 3: Commutative Law

Set up the strips and board as in Presentation 1.
Ask the child if they want to make 8, 10, or 12.
Example for 10: Start with the blue 1 strip and the child will count and place the red 9 strip.
The child will continue to find all the ways to make 10.
Point to the strip 1+9 and the answer and have the child recite it. In the same manner as the previous presentation.
Point to the bottom pair 9+1 and have the child read it.
Explain they are the same. Pull down the lower pair to the bottom on the board.
Repeat for the other pairs, pulling down the lower.
Explain that the problems on the top are the ones we want to remember and write and the ones on the bottom make the same answer so those do not need to be written.
The child will write them in the book and then clear the strips.
Show the child Chart II. Ask what the child notices about the chart. Explain that the empty spaces represent the equations that were pulled down to the bottom of the board.
Have the child locate their equations, read them aloud and verify them in the book.
Note: If the child is unable find their equation on the chart, inverse the addends and they will find what they need. This is reinforcement of the Commutative Law.

Control of Error: Addition Control Chart II

Pedagogical Notes:

The red line at 10 is like the counter in the Snake Game that is laid down at 10. It shows ten and however many more.
When they are recording their answers, their book should not be on top of the board.
The Commutative Law for addition: commutative law, in mathematics, either of two laws relating to number operations of addition and multiplication, stated symbolically: a + b = b + a. From these laws it follows that any finite sum or product is unaltered by reordering its terms or factors. www.britannica.com
We do not do a number plus a zero for two reasons:
1) The rule is to use two strips.
2) Any number plus zero is not an essential combination to be memorized.
The segmented red strips can help the child to count. The blue is the “whole” and then the child can count the segments
Now the right answer is necessary. The child needs to memorize correct facts.

Addition Snake Game