…wooden stamps of four types:
……green unit stamps printed with the numeral 1,
……blue tens stamps printed with the numeral 10,
……red hundred stamps printed with the numeral 100, and
……green thousand stamps printed with the numeral 1000
…box with three compartments each containing 9 skittles and one counter in each of the hierarchic colors;
…four small plates
Again using the work cards, the child does a subtraction. The first number is formed, and from this number a second quantity is taken away and assembled in columns well below the first group. When the child sees that a change is necessary, the stamp of the higher order is placed between the rows as ten of the lower order are counted out. The ten are then placed in the row, the other stamp is put back in the box. When the subtraction is complete the child reads the result-what was left behind. The problem is recorded in his notebook
Would you like to see how we can check to see if you did the subtraction correctly? We can put these two quantities back together. The stamps are counted and changed. ‘Did you get your original number?’ That means that the subtraction was done correctly.
The child should also have practice subtracting with zeros in the subtrahend.
ex. 4000 – 785 =