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