# How to Use an Abacus

An abacus is an ancient mechanism that was used to calculate numbers. The abacus uses two sections; one which is above of the other which both consists of columns that contain beads. In today’s world the scientific calculator is in use and is much more effective; however through history the abacus has been recognized for starting off the calculations of the early mathematicians.

• An abacus

## Instructions

1. On the abacus, the beads to the lower section are assigned certain numerical values. So for example you can assign the rightmost column a value starting from 1 and further to the left you can assign down to the value of 10 and further on again, 20 and so on and so forth until it reached an end value. The beads in the upper part are worth five times the value of the beads in the lower part.
2. To start calculating numbers, start with the beads at the bottom and tilt the abacus towards yourself and allow the beads to fall to the bottom. The lower section of the abacus would have five (5) beads in each row and the upper section would have one or two beads in each row.
3. Input the first number you want to calculate with the abacus and then break it down into single digits. So if for example you want to calculate the number 28, break it into 2 tens and 8 ones (unit). Move from the tens column, a number of beads equal to the tens digit, In this case the number is two and then start moving from the units column, a number of beads equal to the units digit. Notice that in this example that number is 8, and there are only five (5) beads. To overcome this problem, move one bead up from the upper part of the abacus, this bead would now be equal to 5 and then just move 3 more beads from the lower part.
4. Put in the second number that you would like to add or subtract. If you decide to subtract the second number, break down the number into digits exactly like above (10’s and 1’s) but bring down the beads from the ones already above. If you want to add the number, divide the number into digits just like above and move the beads up further in addition to those already up.
5. After this is done, find the total of both numbers by counting the number of beads that is in all the columns. The number you receive will be the result of the calculation. If the value of any digit exceeds nine (9) subtract ten (10) from the value and add 1 to the digit at one larger place value. For example, if you get two (2) in the hundreds position, 13 in the tens position and I in the ones (unit) position, subtract 10 from the 13 in the tens position and add 1 to the 2 in the hundreds position. The result of this calculation will be 331.

## Do’s and Don’ts

• If you are calculating decimals with the abacus, move the unit columns to the left.
• If you are calculating numbers where the unit value is insignificant due to the large magnitude of the number, you can move the units column to the right (out of the abacus).
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