Tuesday, 14 October 2014

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Montessori Activity: Dynamic Subtraction with Golden Beads - Ten Place Value



AGE: 5.5 years old

OBJECTIVE: To introduce the child to double digit dynamic subtraction by exchanging and breaking bulk.

MATERIALS:

1. 19 unit beads
2. 9 ten-bars
3. 1 double digit addition worksheet
4. 3 felt pieces
5. 1 pencil and eraser

PRESENTATION:

1. Arrange the materials according to the picture above.

2. Invite your child to read the first equation or you can also read it together, for e.g. 41+3=?

3. Point to the unit place value of the minuend in the worksheet and ask, "How many units are there?" Your child should answer 1.

4. Take 1 unit bead and place it on the felt piece to the right of the worksheet.

5. Next, point to the ten place value of the minuend and ask, "How many tens are there?" Your child should answer 4 tens.

6. Take 4 ten-bars from the first felt piece and place it on the right felt piece to the left of the selected unit beads.

7. Point to the subtrahend and ask, "How many are there?" Your child should answer 3. Say, "1-3 is not possible without exchanging. You cannot break the ten-bar, but you can exchange it for 10 loose unit beads. 1 ten-bar is the same as 10 unit beads."

8. Put back 1 ten-bar to the left blue felt and exchange for 10 unit beads from the left green felt.

9. Say, "Now you have sufficient unit beads to take away 3" and remove 3 unit beads down the felt piece on the right.

10. Ask your child to count the remaining golden beads left on the top of the right felt. Your child should answer, "38" and write the number on the ten place on the worksheet.

11. Read out the question and answer together, for e.g. 41+3=38

12. Invite your child to try with the next equation.

ADDITIONAL INFORMATION:



REFERENCES:

Place 41 golden beads on the right felt


Say, "It is impossible to take away 3 from 1, but you can exchange a 1 ten-bar with 10 unit beads"


Place the 10 unit beads on the right felt in place of a ten-bar

Say, "Now you have enough unit beads to take away 3" and move 3 unit beads down the left felt

Count the remaining beads left on the top of the right felt, and your child should say, "38". Prompt him to write his answer down on the worksheet and say, "41-3=38"

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