Subtraction Strip Board~ first and second presentation. Montessori Mathematic Lesson (AMI version)

Subtraction Strip Board
with Chart 1
Prerequisite:
Subtraction Snake Game • Subtraction Snake Game...
Material: www.nienhuis.com/us/en/subtra...
A board divided into 18 squares horizontally and 12 squares vertically. Each square is 2 x 2 cm. Above the grid are the numbers 1 to 18 (1 to 9 in blue and 10 to 18 in red). A blue line divides the board vertically after the 9.
2 sets of numbered strips - one blue set with numerals in red (1-9) at the end of each strip and one red set divided into squares by blue lines with numerals in blue (1-9) at the end of each strip.
17 strips of plain wood (not numbered) from 1 to 17 in square lengths.
Prepared subtraction booklet
Pencil
Subtraction Control Chart 1
First Presentation:
Invite the child
Introduce the activity and the material
Show the child how to carry the material: carry the board as a tray with the two strip box on top
The guide or the child also brings the writing tray with the subtraction tablet booklet, pencil and pencil holder
Show the child and say: the numbers on the top from 1 to 18 are the minuend (the first part of the sub equation)
Also say: There are some numbers from 1 - 9 in blue, we always find our difference in blue numbers. The blue line reminds us the answer or the difference would always be in blue numbers
Take out the blue strip from the box and tell the child: we are just going to work with the blue strip right now
Leave the red strip in the box
Arrange the blue strip from 1-9 in order on the left corner of the board, start with 1.
Take out the brown strip and arrange them in sequence from 1-17 on the left side of the board with the number 1 strip align with the bottom of the board
Open the booklet and open the first page and invite the child to read the first equation: 18 - 9 =
Point out on the board the number 18, say: this is our minuend,
Take the blue strip of 9 and say that this is our subtrahend and place it over the top of the number starting from the right of the board (so it covers all the numbers from the right)
Say: the difference is always the number to the immediate left of the blue strip
Invite the child to write the difference
Put the strip back on top
Continue to the equation on the next page
Read the equation 17 - 9 =
Say: our minuend is 17 so we are going cover 18, place the shortest brown strip and place it over 18
Take the blue strip 9 and place it over from 17, the child will see that the difference is 9
Invite the child to read the answer : 17 - 8 = 9 seventeen minus eight equals nine
Continue as the same manner
Invite the child to continue complete as many as he likes
Put back the blue strips
Invite him to write the equation
When he’s done invite him to check how work with control chart one
Show him how to put away the blue strip and the brown strip as the same manner as the strip board
Second Presentation:
Writing the subtraction table
This time invite the child to bring the strip board
Set up the blue strip, the red slip and the brown strip
On the tray: protector, a grid paper, a pencil and a pencil holder
Invite the child to choose a number between 6 to 8
The child say: 8
Take a brown strip and cover all the number on the board from 18 - 9, until you see 8, in order to isolate the number you are going to work. To do it: you count the brown strip from the top to bottom to find the correct brown strip
Take the strip 8 and place it on the first grid row
Tell the child: we are going to work with the subtraction table of 8, and we write 8 on the paper at the top
Say: we are going to start making 8
Take the red strip 7 and place it under the first red strip 8 and tell the child: How many more we need to make 8?
The child say: 1
Take the blue strip 1 and place it next to the red strip 7 to make 8
Do the same thing with the next number: ex: red 6 with blue 2 ….
The last one that you put, is going to be blue strip 8. Place the blue strip 8 at the end.
Start pointing at the bottom of the blue strip, say: here we have 8, if we take 8 from 8 (while sliding down the blue strip), what do I have? Point at the blank space. The child will say: zero
Invite the child to read the equation: 8 - 8 = 0
Invite the child to record the equation: 8 - 8 = 0
Remove the blue strip and place it back
Do the same with the rest until no more blue strip to take away
Say: If I have 8 and take away 7 while sliding down the blue 7, how many I have left (while pointing to the red strip)
When the child finish a paper, check with the subtraction control chart 1
When the child has finished, invite him to choose another number to work with
When he finish working, show him how to put the material away: start with putting the blue strip 9 with the ribbon . Put the brown strip back in the box, start with the longest, do not force them in
Direct Purpose:
To help the child memorize the basic combination of subtraction
To demonstrate that subtraction is opposite to addition
Age:
5 1/2