The Stamp Game: Dynamic subtraction (with change)

How is this activity presented?

The directress introduces the expanded notation card to the child and reminds him about the (-) sign. She reads the operation to the child (4364 - 3177) and reminds him how to form a number with the stamps. The directress reminds the child to only take out the minuend (top number) from the stamp compartment, and subtract the subtrahend (bottom number).

The directress takes out the corresponding amount of unit stamps and places them vertically to the right of the mat. She shows the child how to set out the tens to the left of the units, followed by the hundreds and thousands. She then shows him how to take the quantity of the subtrahend from the stamps.

She begins with the units and the child then realizes that seven units cannot be taken away from four units. The directress reminds him that they can exchange one ten for ten unit stamps. The child then replaces one ten for ten units and places them in the unit column. The child now realizes that they can take seven units away as they now have14 unit stamps. The child records the answer in the correct column, with the correct coloured marker.

The directress then shows the child how to subtract the tens, but realizes they do not have enough tens to subtract seven tens. The child then exchanges one hundred for 10 tens and places the tens in the correct column. The child records the answer with the correct coloured marker in the correct column.

The child continues in the same manner with the hundreds and thousands, exchanging if necessary and recording the answer in the correct column in the correct coloured marker.

What does the child learn by doing dynamic subtraction with the stamp game?

This activity reinforces place value in the decimal system, it reinforces the (-) sign and gives the child a better understanding of the process of subtraction using more abstract materials.

Looking for more Montessori activities?

Here is a list of all the Montessori Maths activities including Early Maths, Introduction to the Decimal System, Seguin Boards, The Hundred Board, The Short Bead Stair, Bead Chains, The Snake Game, Group Operations, The Large Number Rods, Recording with the Small Number Rods, The Short Bead Stair, The Strip Boards, The Boards, The Stamp Game, The Abacus, The Dot Game, and Fractions. Just click on the page you want to learn about to go there.