Subtracting by Grouping
Direct Addition
Direct addition can take place when a digit needs to added and all of the beads are available. One motion of your hand will complete the addition. Click on the link, Direct Addition, to learn this skill.
Direct Subtraction
To directly subtract a number or a digit in a number, the all the beads need to be present in the column. Click on the link, Direct Subtraction to learn this skill.
Adding with Five Extras
The first basic lesson you should learn is how to add a number to a column when all the beads below the bar have been pushed to the bar. We call this Adding with Five Extras since it involves using the 5 bead. Click on this link above to study this technique in detail.
Subtracting with Five Extras
The next basic section (lesson) covers how to Subtraction with Five Extras . Click on the link above to start the lesson. We suggest that you become familiar with this approach before continuing to the next section.
Subtracting with Ten Extras
Unfortunately, not all subtraction calculations can be completed correctly by simply clearing beads directly. In some of these situations, when the 5 bead is available, you can use the five (5) extras principle. You learned this principle in the previous section. However, when the 5 bead isn’t available, you will need to apply another principle, the ten (10) extras principle. That’s the principle we will discuss in this section. Click on the link Subtracting with Ten Extras to begin learning this principle.
Subtraction with Five Extras and Ten Extras
In this section, you will apply both the five (5) extras principles of addition and subtraction and the ten (10) extras principle for subtraction to integer subtraction calculations. But before you “put it all together”, let’s review the five (5) extras principles that were covered in the previous section. Click on the link Subtracting with Five Extras and Ten Extras to review and build your subtraction skills.
Subtracting Decimals and Columns of Decimals
Lastly, we will discuss how to set a decimal number in a Cranmer abacus. Then we will apply the principles from the previous subtraction sections to subtract decimal numbers. Click on the link Subtracting Decimals and Columns of Decimals to complete your subtraction skills.
Abacus Subtraction by Grouping Text
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