Friday, October 4, 2013
Subtraction Strip Board: Analysis of Number
Take a good look because you are not likely to see it here again...the only variations of the subtraction strip board for which we use ALL THREE colors of strips. Montessori R&D calls these presentations "Analysis of Number." We start by establishing a minuend of nine (with the natural wood strips). Then you analyze nine by forming all possible subtraction equations in order with progressively decreasing subtrahends (blue strips). Normally when we use the subtraction strip board we leave the red strips that represent the differences (R&D likes to keep it confusing by calling these remainders) in the box. However in this instance using the red strips highlights the purpose of the presentation: as the subtrahend increases the difference decreases.
Me Too spontaneously combined R&D's "Presentation Three: Analysis of Number, Units" with "Presentation Five: Zero" by insisting on including 9 - 0 and 9 - 9. These are normally excluded from presentation three.
Just a note: I use the Montessori by Hand albums for primary math. However, I use the R&D "Mathematics Manual 1" presentations for the memorization sequences for each operation. The one exception being that I add a snake game to the beginning of each operation as is done in the MBH album.