## Thursday 26 February 2015

### Montessori Activity: Stamp Game - Dynamic Subtraction

AGE: 5.5 years (after the child is familiar with the decimal system, Static Subtraction With Golden Beads and Dynamic Subtraction With Golden Beads)

OBJECTIVE(S):

To teach subtraction without using golden beads.

MATERIALS:

1. Stamp Game
2. Subtraction worksheet
3. Pencil and eraser
4. 1 mat (optional)

PRESENTATION:

7325
- 5956
--------
?
--------

2. Arrange the stamps showing the minuend e.g. 7325

3. Point to the unit place value and explain that it is not possible to subtract 6 from 5 without exchanging the stamps.

4. Exchange 1 blue ten stamp with 10 green unit stamps from the bank and place the 10 green unit stamps together with the unit stamps.

5. Keep track of the exchange by counting the remaining blue ten stamps (now 1) and green unit stamps (now 15).

6. Indicate on the worksheet by crossing out the number 2 in the ten place value with 1 and writing 1 in front of the 5 unit place value indicating that there are now 15 unit stamps.

7.  Subtract 6 green unit stamps from the now 15 green unit stamps and return them to the bank.

8. Count the remainder and write the answer 9 in the unit place value.

9. Point to the ten place value and explain that it is not possible to subract 5 from 1 without exchanging.

10. Exchange 1 red hundred stamp with 10 blue ten stamps from the bank and place the 10 blue ten stamps together with the ten stamps.

11. Keep track of the exchange by counting the remaining red hundred stamps (now 2) and blue ten stamps (now 11).

12. Indicate the change on the worksheet by crossing out the number 3 in the hundred place value with 2 and writing 1 in front of the 1 ten place value indicating that there are now 11 ten stamps.

13. Subtract 5 blue ten stamps from the now 11 blue ten stamps and return them to the bank.

14. Count the remainder and write the answer 6 in the ten place value.

15. Point to the hundred place value and explain that it is not possible to subract 9 from 2 without exchanging.

16. Exchange 1 green thousand stamp with 10 red hundred stamps from the bank and place the 10 red hundred stamps together with the hundred stamps.

17. Ask your child to keep track of the exchange by counting the remaining green thousand stamps (now 6) and red hundred stamps (now 12).

18. Indicate on the worksheet by crossing out the number 7 in the thousand place value with 6 and writing 1 in front of the 2 hundred place value indicating that there are now 6 green thousand stamps and 12 red hundred stamps.

19. Subtract 9 red hundred stamps from the now 12 red hundred stamps and return them to the bank.

20. Count the remainder and write the answer 3 in the hundred place value.

21. Subtract 5 green thousand stamps from the now 6 thousand stamps and return them to the bank.

22. Count the remainder and write the answer 1 in the thousand place value.

23. Read out the question and the answer again and verify by counting the stamps:

7325
- 5956

--------
1369
--------

VIDEO DEMONSTRATION:

Our Little FECS (5Y11M20D) tried this for the first time today 25 Feb 2015. He was very tired and still jet lagged from our trip back from Singapore. He understood the concept, but required step-by-step prompting. It was a little wasted work. I will have repeat this again.

Our Little FECS tried this again on 17 August 2015 (6Y5M11D). He was able to do the first sum, but found it a little challenging with 703 - . For a moment, he got stuck with the "0" in 703. But this time around, it has been better than the first time, and practice makes perfect. He found division with remainer easier than dynamic subtraction.

REFERENCES:

The stamp game is available from Amazon:

 2. Arrange the stamps showing the minuend e.g. 7325

 3. Point to the unit place value and explain that it is not possible to subtract 6 from 5 without exchanging. 4. Exchange 1 blue ten stamp with 10 green unit stamps from the bank and place the 10 green unit stamps together with the unit stamps.

 5. Keep track of the exchange by counting the remaining blue ten stamps (now 1) and green unit stamps (now 15).

 6. Indicate on the worksheet by crossing out the number 2 in the ten place value with 1 and writing 1 in front of the 5 unit place value indicating that there are now 1 blue ten stamps and 15 green unit stamps.

 7.  Subtract 6 green unit stamps from the 15 green unit stamps and return them to the bank.

 8. Count the remainder units and write the answer 9 in the unit place value

 9. Point to the ten place value and explain that it is not possible to subract 5 from 1 without exchanging. 10. Exchange 1 red hundred stamp with 10 blue ten stamps from the bank and place the 10 blue ten stamps together with the ten stamps.

 11.  Keep track of the exchange by counting the remaining red hundred stamps (now 2) and blue ten stamps (now 11).

 12. Indicate the change on the worksheet by crossing out the number 3 in the hundred place value with 2 and writing 1 in front of the 1 ten place value indicating that there are now 2 red hundred stamps and 11 blue ten stamps.

 13. Subtract 5 blue ten stamps from the now 11 blue ten stamps and return them to the bank.

 14. Count the remainder and write the answer 6 in the ten place value.

 15. Point to the hundred place value and explain that it is not possible to subract 9 from 2 without exchanging. 16. Exchange 1 green thousand stamp with 10 red hundred stamps from the bank and place the 10 red hundred stamps together with the hundred stamps.
 17. Keep track of the exchange by counting the remaining green thousand stamps (now 6) and red hundred stamps (now 12).
 18. Indicate the change on the worksheet by crossing out the number 7 in the thousand place value with 6 and writing 1 in front of the 2 hundred place value indicating that there are now 6 green thousand stamps and 12 red hundred stamps.

 19. Subtract 9 red hundred stamps from the now 12 red hundred stamps and return them to the bank.

 20. Count the remainder and write the answer 3 in the hundred place value.

 21. Subtract 5 green thousand stamps from the now 6 green thousand stamps and return them to the bank.

 22. Count the remainder and write the answer 1 in the thousand place value.

 23. Read out the question and the answer derived again and verify by counting the stamps i.e. 1369.

 25 Feb 2015 (5Y11M20D) - Our Little FECS tried this for the first time today

 15.4.2015 (6Y1M10D) - Our Little FECS got it right without much supervision today :-)