Sean-Paul has taken off in leaps and bounds with his math this year thanks to a very few Montessori presentations and a handy used workbook I picked up over the summer for $2.00 :)
Pictured left is an equation completed with the Subtraction Board (ours is from Alison's Montessori, although not this expensive version, mine was only $15 at the time of purchase). Here is another version at Kid Advance. You can also acquire a printable version from Montessori For Everyone.
So, on to the lesson. The board numbered across the top 1-18 and covered with a grid twelve deep comes with a set of numbered and divided red strips 1-9, blue numbered strips 1-9, and un-numbered white strips lengths 1-18. The example shown above is for the equation 5 - 2 = 3.
Here is how I present the lesson:
- First we say the equation out loud and read as follows, "Five take-away two."
- Next he locates the red numbered strip that corresponds to the "Minuend" (or the number to take away from) which in our equation is "5" and removes the corresponding white strip. He then places that strip across the numbers at the top of the board to cover from 18 to 6. Now the blue five is showing down to one.
- Now he selects the red strip "Subtrahend" or the take-away digit which in this equation is the "2" and places it directly under the blue "5" in the first row.
- The difference of the two numbers is the empty space which he will fill with a corresponding blue strip to give our answer of "3".
To complete the equation he repeats that "Five take-away two is three" and writes his answer into his workbook; then replaces the strips back into position on the board to begin another equation.
This is a very satisfying way for the children to see subtraction in action and it reinforces that it is also another way to show addition at the same time. I always mention after they finish each equation to "check" their work and by looking at the strips all placed together that they indeed add back up to the original minuend. In our case 2 + 3 = 5 and so forth.
Here he has completed 5 - 4 = 1, a very happy math boy :)
Please email me or ask questions in the comments if you'd like more information or help setting up a Montessori Math Center, it is well worth your time and effort and so much great learning for the kids!!
Many blessings in your day, happy Feast of St. Francis of Assisi!!