As for addition, but including a fourth set of small cards to 9000 and a small mat to put those cards on.
Specify the vocabulary: minuend, subtrahend, and the different.
- Invite three children to come and work with you.
- Set up the material as in Addition, including the new set of cards. This new mat should be placed next to the large mat with the large number cards.
- Take the directress tray and with the children, go over to the Supply Mat.
- Ask one child to put 7 units into the dish on the tray.
- Ask another child to place 8 tens onto the tray.
- Ask another child to place 7 hundreds on the tray.
- Ask another child to place 9 thousands on the tray.
- Emphasize that you have a lot of beads on your tray.
- Take the tray back to the large mat.
- Ask each child to count the units, tens, hundreds, and thousands. Have each child get the corresponding card after each is counted.
- Supper impose the cards to get: 7879
- Have each child take their trays to the small mats and tell them each what to get. For example:
3 units, 2 tens, 4 hundreds, and 3 thousands
2 units, 4 tens, 5 hundreds, and 6 thousands
1 unit, 3 tens, 4 hundreds, and 5 thousands
- Tell the first child that you are going to give him some of your beads.
- Ask his how many units his card asks for. (3)
- Have him count three from the directress’s tray and place it into his own dish.
- Repeat for the tens, hundreds, and thousands.
- Have the child superimpose his cards and read it with the others: 3 units, 4 tens, 2 hundreds, and 3 thousands. Then read, 3423
- Ask, “Do I still have 7879?” No!
- Move the cards 7879 up to the top left corner of the mat.
- Ask one child to count how many beads you have left and choose the new small cards to mark each set of beads.
- Have the child superimpose the cards to read: 4456.
- Say, “So let’s see what we did here. We started off with 7879 but then I gave some away.” (Ask for the first child’s cards and place them below 7879.) “I gave away 3423. And in the end, (place the new total below 3423) I ended up with…4456 beads.”
- “And this is called subtraction!"
- Give the cards back to the child to replace and have him give you back the beads.
- Beginning at when you started with 7879 beads, repeat the subtraction for the second child.
- Once done, begin again at 7879 and repeat the subtraction with the third child.
- Once each child has had a turn, say: “What we have just done is subtraction. I had a lot of beads and you took some from me so I no longer had the same amount of beads.”
- Done as in the above presentation.
- The only different is you will have to change, just as in Dynamic Addition.
This is done in the same way as in the above presentation but this time, the first child will take some of your beads away, the second will take from what is left of the directress tray, and the
third child will take from what is left after that.
(Photo shows this in process.)
After the first quantity is taken from the original pile, place the large number cards at the top left corner of the mat. Place the small cards from the child below it. Keep placing the cards in this manner after each child take some of the beads away.
(See photo to the side)
To give the impression of the nature of subtraction and how it differs from addition, in this case:
- One starts with a capital and people come to fetch from it, by bringing an empty tray and the demand expressed in small cards.
- One has to break up a unit of the larger category into ten of the smaller one.
- A larger quantity is divided into 2 or more smaller different ones.
- Generally something is left over for the one who had the original number.
The directress verifies at first. Then she shows that if all the smaller numbers that were taken away are added together, they should amount to the original number.
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