Content

• To step
• Tips

It abacus is a very old calculator that was used all over the world. Today they have been replaced by calculators, but it is still a lot of fun to use an abacus. Read on to find out how to add and subtract ... the old-fashioned way.

To step

1. Understand how an abacus works. The abacus consists of two parts one above the other. Each section consists of rows of beads. The bottom part usually consists of five beads and the top part usually consists of one or two beads.
   1. The beads in the lower part are assigned certain values. For example, you can assign the value 1 to a bead in the right row. Then you assign the value 10 to the next row, to the left of the first row, and the value 100 to the next row, and so on.
   2. The beads in the top section are worth 5 times more than the beads underneath.
2. Start with the beads at the bottom. Tilt the abacus so that all the beads fall down. The five bead section should always be below the two bead section.
3. Enter your first number.
   1. Divide the number into separate numbers. For example, divide 28 into 2 tens and 8 units.
   2. In the row of the tens, move two beads upwards. In the same way, you have to slide eight beads up in the unit row. Since there are only five beads in a row, first slide one bead up in the top part. This bead represents 5. Now you only have to move 3 beads in the bottom part.
4. Enter the second number. The way of entering depends on whether you are adding or subtracting.
   1. If you want to add up, you can divide the number into two digits as explained above and then slide the corresponding beads up.
   2. If you want to subtract, divide the number again as above, but slide beads down instead of up.
5. Count the total. Count the number of beads in each column. This will give you the value of each decimal. If the value is more than nine, subtract 10 from this value and shift 1 bead in the row of the larger decimal. For example, you get 2 in the hundreds row, 13 in the tens row and 1 in the unit row. Then subtract 10 from the 13 in the tens row and add 1 to the 2 in the hundreds row. This gives the result 331.

Tips

• If you are dealing with numbers below 1, you can move the units column to the left so that you get a row for every decimal place.
• Or if you are dealing with numbers where the unit value is irrelevant due to the size of the number, you can move the unit row to the right (outside the abacus).
• The abacus does not calculate anything for you, but it helps you keep track of the numbers.