Montessori Mom

• Subtraction
• Age: 6 and older

2. Purpose:

Teach the concept of zero, negative and positive numbers. Teaches concrete concept of subtraction as well as the higher levels of algebra- equations of equal quantity and making the computation functions the same.

3. Materials:

• A box of colored bead bars
• A box of golden ten bead bars
• A box of gray wooden negative bead bars-sets containing 1 through 9. (Provide the same amount of gold, colored, and negative bars for the First Lesson.)
• One set of black and white bead bars-1 through 9.
• 2 empty boxes
• Pencil or pointer
• A cloth or felt mat or cloth place mat

4.Presentation:

Spread a rug or long mat on the floor. (I like to do this where the child has lots of room to work.) Put the negative and colored bead bars boxes next to each other side at the upper corner of the mat. Put the black and white beads in a triangle stair with the box of gold ten beads next to it at the other corner.

(In this lesson the colored bead bars are added, the black and white bars are remainders, and the negative bars are subtracted.) Arrange the snake with the colored bead bars as you did in the positive snake game. Continue on the colored bead snake with the same quantity negative bead bars.

4.1. Here is an example:

(You need only one colored bead bar stair[1-9], one negative bead bar stair[1-9], the black and white bead bar stair[1-9], and 4 golden ten bead bars)

1. Arrange the colored bead bars and negative bead bars like this: 1+8+2+5+6+9+3+4+7-3-5-6-1-8-2-9-4

(+are the colored bead bars - are the negative gray bead bars)

2. Count the colored bead bars, beginning at one end of the snake (left to right). Count until 10 is reached. Put down the pencil point at 10. (The example would be one in at the 2 bead bar) Replace the colored beads with the golden ten bar and the 1 black bar. Put the colored bead bars in an empty box. Continue counting the colored bead bars until the snake is all golden 10 bead bars and the last black and white bar. (For the example, these have 4 golden bead bars and a 5 black bar bead) (This is just like the Additon Snake Game)
3. Now the first negative bar is finally reached. In the example, it will be negative 3. Tell your child that 3 must be taken away from the 5 black bead bar.
4. Count backward to 3. Replace the 5 black bead bar with a 2 black bead bar. Put the negative 3 bead bar in the empty box.
5. Next point to the negative 5 bead bar and count backwards to 5. The pencil point will be touching the 3rd bead of the golden 10 bead bar. Tell your child this time you will have to replace the black bead bar and golden bead bar. Put the 5 negative bead bar in the box.
6. Replace the 10 gold bead bar and 3 black bead bar with a 7 black and white bead bar. Put the gold bead bar and 3 black bead bar back in their place by the edge of the mat.
7. Continue in this manner until all the beads have been removed. The snake is now gone.

5. Checking your work exercise:

Put each respective bead bars in a triangle stair- the colored bead bars together -the negative bead bars together Match the negative beads to the positive beads.

6. Try this:

Using a 5 colored bead bar and a negative 5 gray bead bar; Point to the 5 colored bead bar and say “ 5”, and put the negative gray 5 bead bar next to it, “take away 5 is 0.” Continue with the other bead bars.

7. Terms to introduce:

• Subtract
• Remainder
• Negative
• Positive
• Zero
• Add