The subtraction strip board – MONTESSORI

Materials

The subtraction strip board
Blue strips 1 to 9
Red strips with partitions 1 to 9
17 unmarked wooden strips
Prepared subtraction tables
Pencil
Subtraction chart 1
Using the Subtraction Strip Board, the child practices the equations of the subtraction tables 1–18. Natural wooden strips corresponding in length to the squares 1–18 are used to indicate the number to subtract from (minuend) and 1 set of blue strips used to subtract with (subtrahend). A set of red strips is included for further explorations. The 2 sets of strips are stored in hardwood boxes

Recommended Age: 5 years and onwards (can be younger depending on the child’s skills and experiences)

Purpose: To practice subtraction that will lead to memorization of the essential subtraction combinations

Level of Parent Involvement: Medium, the adult must present this exercise to the child, once the child has been shown they may work independently

Prerequisites

The child must be able to count accurately from 1-10 and onwards
The child must be able to write numbers
The child must be able to match the numeral symbol with its quantity of numbers 1-10 and beyond
The child must have had many experiences doing subtraction with the golden beads.

Preparation

Invite the child, introduce the subtraction strip board, the child may bring the materials to the table
Notice with the child the different coloured numbers on the top of the board
Lay out the blue strips from longest to shortest on the left side of the board
Introduce the child to the unmarked wooden strips, begin placing them in order from longest to shortest to the right of the blue strips
Do a few then the child may finish laying them out
Invite the child to choose their favourite number for example 12

Then, using one of the unmarked wooden strips, blank out the numbers from 13-18 informing the child they don’t need to remember the red numbers
You may show the child to count the strips from longest to shortest 1,2,3…12 and take that strip and place it on the board to cover the numbers you don’t need
Then ask the child “how many do you want to take away from 12?” indicating towards the blue strips
Child responds 9 for example, place the blue strip of nine to the left of the unmarked wooden strip informing the child the answer is at the end of the blue strip

Repeat a few more times, then invite the child to practice
Let the child know if the answer is red we don’t need to write it down or remember it

When the child has had sufficient practice, introduce them to the prepared subtraction tables
Invite the child to choose another number and use the blue strips to find the answers
At the end introduce control chart 1 to check.