How to Introduce the Montessori Decimal Board: A Step-by-Step Guide Part 1

Teaching decimals in Montessori becomes much easier when children can see and manipulate what tenths, hundredths and thousandths actually mean. The Montessori Decimal Board is a hands-on maths material that helps children connect their earlier understanding of fractions and place value with decimal notation. Decimals can be difficult because children often have far less everyday experience with numbers smaller than one than they do with whole numbers.

Yet a strong understanding of decimal place value is essential for later work with fractions, percentages, measurement and more advanced mathematics. In Montessori elementary maths, the Decimal Board allows children to explore this abstract idea concretely. Children can see the relationship between one whole, one tenth, one hundredth and one thousandth, while connecting each quantity to its written decimal form.

In this first lesson, I’ll show you how to introduce the Montessori Decimal Board, what knowledge children should have beforehand, and how to use the material to build a clear understanding of the relationship between fractions and decimals.

For the second article in this series click here 

The lesson - Introduction 1

Prior to this lesson students will need to

• Have a very secure knowledge of fractions
• Have a secure knowledge of ten e.g. ten units make ten, ten tens make one hundred

You will need to have a premade fraction strip to place on top of the decimal board.

As an alternative you can use this freebie:

1) Place a green bead, golden bead and red circle inset (fraction circle) ask what these all are (1).

2) We are going to work with this green bead and pretend we are going to cut into 10. Why 10? (have students answer)

3) Show the blue disks and say these are each one tenth - point to the fraction strip at the top to show this

4) Take one tenth. Ask what it would be if I cut into ten bits (100ths) show the red/dark pink disk and say how these equal 100ths - point to the fraction strip at the top to show this

5) Continue across dark green: thousandths, light blue: ten ten-thousandths, light pink: ten hundred-thousandths, light green: ten millionths.

The lesson - Introduction 2

1) Produce a red bead. In the stamp game/checkerboard what is red? (hundreds) . 

2) If I exchanged it what would I exchange it for? (ten blue beads - tens) . Ask a student to make this exchange. 

3) Repeat with the blue beads for the ten green unit beads. Have a student exchange them. 

4) Continue going into the 'decimals' make sure students know that 'th'goes at the end of the decimal words. It may be useful to over accentuate this sound so students hear it. 

5) Students can ask a partner to 'exchange' a number for a number. 

The lesson - Introduction 3

1) There is a number that we use a lot in maths. That number is the unit. Show the golden bead unit/ red whole fraction/ green bead. 

2) We are going to use the green bead to show units today. We have been using this green bead when we use the decimal board. 

3) Place the green unit bead in the units column

 

4) Ask students what it stands for (1)

5) What is the number immediately to the left of this unit bead? (10)

6) What is the number immediately to the right of this unit bead (a tenth)

7) What do you notice about the numbers on either side of this unit? Put one finger in the tens and another finger in the tenths. (They both have the word ten in it) 

8) Now point to the hundreds and the hundredths. What do you notice about these numbers? (They both have the word hundredths in them) 

9) If possible place a laminated sheet or similar over the top of the decimal board and draw with curved lines the connections between the numbers e.g. draw a curved line that connects the tens to the tenths, another line that connects the hundreds to the hundredths, another line that connects the thousands to the thousandths and so on....

10) Conduct a three period lesson for the names of the numbers.

 To see what comes next go to the second article in this series here