Subtraction

Stamp game

Age:6-8 (*Must be familiar with Golden Bead subtraction)
Objective: Further abstraction of the concept of subtraction by subtracting large numbers.
Method: A number in the thousands is formed with the stamp game. The subtrahend is then taken away and put back, starting at the 1s, then the 10s, 100s, and 1000s. If the minuend has insufficient 10s to take away those required by the subtrahend, break one of the 100s into ten 10s, etc.
Materials: A quantity of small squares in green, blue, and red. If helpful, label the green ones with “1,” the blue with “10,” the red with “100,” and more green ones with “1000.”
Link: https://www.youtube.com/watch?v=YB9RI4_H7O0

Age: 6-8
Objective: Further abstraction of subtraction math facts.
Method: The two staircases are laid out on either side of the board. A blank strip is placed on the board to establish the minuend. The minuend is taken from the blue stair and placed on the board starting at the end of the blank strip, and the answer is taken from the red stair and placed in the remaining strip. The answer is the red strip. Many problems are done.
Materials: Strips of cardstock from 1 cm to 9 cm, one set in red and another in blue. An 18 cm chart with each cm labeled (1 to 18). A 17 cm blank strip (not red or blue).
Link: https://www.youtube.com/watch?v=3pLWxgiJpR4

Age: 6-8
Objective: Movement towards memorization of basic subtraction math facts.
Method: For example problem of 10 - 4 =, the right index finger is placed on “10” on the top row, and the left index finger is placed on “-4” on the left column. The fingers are then slid together to find the answer, “6.”
Materials: Paper chart of all minuends, subtrahends, and answer combinations from 1-9. Can be printed from http://www.montessorialbum.com/montessori/images/1/10/Subtraction_Chart_2.pdf (pages need to be taped together to make complete chart)
Link: http://www.montessorialbum.com/montessori/images/1/10/Subtraction_Chart_2.pdf