Exploring Decimals

After much activity with our fraction material, I decided it was time to create our own Montessori Decimal Board.  In our first lesson, we connected the red 1/10 inset to the decimal 0.1. We began by cutting the first 1/10 into 10 pieces and then attempted to cut those smaller pieces into “10 more pieces.” While some children volunteered to help, we quickly realized the pieces were becoming too small. At that point, a few children referenced our lessons on atoms as they tried to visualize what a thousandth or a millionth would be like.

For most of the children, this was their first experience with decimals, while others had seen decimals before in a more traditional classroom.

As we started, I couldn’t help but think back to my own math lessons years ago, when the teacher would simply say, “line up your numbers and put the decimal point in.” There wasn’t much room to truly understand why it worked that way — we were just told to follow the rule.

Using our decimal board, we built all the way up to millionths — our new decimal colors of pink, light blue, and light green reflect the familiar red, blue, and green color-coded series in our whole number materials.

The students built numbers like 12.456 and learning how to say them: “twelve and four hundred fifty-six thousandths.” 

You could see the light bulbs turning on as they realized how each place on the board represents a power of ten — and how moving one space changes the value completely.

Interested in seeing how a Montessori Decimal Board lesson works?

Here’s a helpful demonstration video that shows the concept beautifully:

https://youtu.be/7k2mqyLmGDY?si=hJeVCVR9ASlJ7EDC