#### Material

Chart 2, showing answers for all the subtraction combinations.

Chart 3, blank for placement of wooden answer tiles.

For each chart, a set of subtraction combinations (tickets) without the answer.

For each chart, a receptacle for completed problem tickets.

For chart 3, a box of wooden squares with the answers.

Chart 1 (control chart) for checking.

Grid paper, pencil and pencil holder.

#### Presentation

##### Chart 2

- Invite the child to the lesson.
- Introduce subtraction chart 2.
- Ask the child to bring the chart and the box of prepared slips.
- Briefly talk about the board:

“These red numbers are what we start with, and these blue numbers are what we take away! And all these numbers in the middle are the answers! I’ll show you how to use it.” - Place your dominant finger on a red number such as 12.
- Place your sub dominant finger on a blue number such as 8.
- “Twelve take away eight is…”
- Slid your sub dominant finger to the right and your dominant finger down until they meet in a box.
- “…four! There it is!”
- Give a couple more examples and ask the child to do some examples as well.
- Bring two papers, underlays, and pencils on a tray.
- Open the box of prepared slips.
- Ask the child to choose a random slip and to read it.
- Write the problem on your paper and ask the child to write it on his.
- Solve the problem using the chart.
- Write the answer on your paper and ask the child to write it on his.
- Place the used prepared slip inside the lid of the box.
- After a few prepared slips have been used, let the child work independently.
- “You can keep working, and when you’re done, you can use subtraction chart 1 to check your answers!”

##### Chart 3

- Invite the child to the lesson.
- Show him Subtraction Chart 3.
- Ask him to bring the board, pencil, paper and underlay to a table.
- Look at the board with the child:

“There are no numbers over here! Just red and blue numbers, but none in the middle!” - Bring the box of prepared slips and the box of tiles.
- Show the child the slips but then close the box again.
- Open the box of tiles and put the tiles on the table.
- Pick out tiles to make a row that goes from 0 to 9.
- Ask the child to organize the tiles with you, in columns based on their number.
- Once all the tiles are organized, admire them.
- “We’re going to put these tiles where they are supposed to go!”
- Take out a prepared slip and read it:

“Twelve minus eight.” - “You know the answer right? Yes, four!”
- Slide a 4 tile down to isolate it.
- Place your fingers in the same positions as with subtraction chart 2, and slide them together in the same way.
- Place the tile on the square where your fingers meet.
- Create excitement and stay with the child as he solves a few more problems.
- “Alright, you can keep reading the slips and placing the tiles!”
- “When you are done, I bet you know which chart to use to check your answers. Right, subtraction chart 2!”

#### Exercises

Child works independently.

#### Direct Purpose

To memorize the subtraction combinations.

#### Indirect Purpose

Preparation for negative numbers.

#### Control of Error

Control for subtraction chart 2 is subtraction chart 1.

Control for subtraction chart 3 is subtraction chart 2.

#### Age

5 1/2 to 6

#### Notes

Underlays are good to have for all boards, as the underlays will go under the board and prevent it from sliding around.