Subtraction Strip Board

Contains 2 versions, the Nienhuis version contains
1a) A chart 18×12 squares with numbers
1b) 9 blue solid or divided strips with numerals 1-9 to subtract with
1c) 9 divided into squares red strips with numerals 1-9
1d) 18 strips to indicate number to subtract from
Teaching Montessori in the home: The school year version contains
2a) A simplified strip board
2b) A 17 square white ruler
2c) 9 divided blue strips with numerals 1-9
Optionally, the red and blue strips can be printed on red and blue paper respectively to save ink.