the virtual abacus
Post on 28-Mar-2015
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USING THE VIRTUAL ABACUS
1. Go to the website - http://nlvm.usu.edu/
2. Click on the grid as shown below:
3. Go to Abacus and click it. You will see a virtual interactive abacus .
4. Each bead represents a unit depending at which column of the abacus. Reading from right to left,
1st column: unit (e.g. 1,2,3, and so on) 2nd column: tens 3rd column: hundreds and so on
5. If you have used all the 5 bottom beads, you can replace it with one top bead.
CLICK HERE
UNITS
TENSHUNDREDS
The 1st picture shows that you have used all of the five beads , therefore, this means that you now can use the top bead which represents a five. As shown in the 2nd picture.
Example: To count six on the abacus, move down one top bead and move up one bottom bead. As shown below:
The picture above shows a 6 where the top bead is a five and the bottom bead is a 1. Notice that there are two top beads in the abacus. For this column, this two top beads represent a ten.
1 top bead = 5 2 top beads = 10
Now, use the abacus to represent the following numbers:
5,7,8,9,10
TENS
6. The 2nd column represents tens, whereby
1 bottom bead = 10.
2 bottom beads = 20. And so on;
Here, for the top beads:
1 top bead = 50 2 top beads= 100
Explore More:
Try to show the following numbers on the abacus:
11, 15, 30
HUNDREDS
7. The 3rd column represents hundreds, whereby:
1 bottom bead = 100. 2 bottom beads = 200. And so on;
The above picture shows a 100.
Here, for the top beads:
10
50
100
1 bead = 500
2 beads= 1000
Explore More:
Try to show the following numbers:
200, 600, 150.
Further example:
127, try it on your own first!
Explanation:
127 = 100+20+7
1. Look at 1st digit to the right of 127 that is 72. Count 7 in the first column (move 1 top bead and 2 bottom beads)3. Now, the 2nd digit of 127 that is 2. Remember that the 2nd column represents tens.4. Count 20 in the 2nd column. (move 2 bottom beads up)5. Next, the last digit which is 1. (Again, remember that the 3rd column represents
hundreds).6. Count 100 in the 3rd column. (move 1 bottom bead).
Explore More:7. Try to show the following numbers:
307, 512, 99, 707
7
20
100
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