As in all Montessori classrooms, the range of math materials the children use is wide. But all of the math concepts and procedures are taught through handling the special materials designed about one hundred years ago by Maria Montessori. They count beads to solve simple addition, subtraction and multiplication problems. They use the division board to solve simple division problems. The Seguin boards show the children the base ten system in our teen and double digit numbers.
The bank game, pictured above, shows the relationships between the units, tens, hundreds and thousands. Eventually many of the children will use the thousand cubes, hundred squares, ten bars and units of the bank game to solve simple and long math problems. When I was a child, I learned to do long addition through memorizing the trick of working from right to left, placing the right digit of a 2 digit answer under the problem's line and carrying the left digit into the next line of numbers to add. It worked, but children do much better when, through the use of the Montessori materials, they discover and understand why.
I'll follow this, soon, showing you the division board and the Seguin boards.