We can also assign a decimal place. If we want to represent a decimal number such as 10.5 then the rightmost column will be the tenth place, earlier it was one’s place and followed by the place of the whole numbers such as ones and tens.
Similarly, by moving the beads towards the reckoning the bar we can make any number.
As the bottom row has only four beads to make a number more than 4, we have to move back the bottom deck’s bead to its original position and bring down the heaven bead towards the reckoning bar.
To make 6 with the heaven beads, you need one earth bead touching the reckoning bar.
Solved Examples on Abacus Subtraction
It is better to understand subtraction using examples. Let us begin with something simple and try to calculate 102-78.
102-78=24
Step 1: Set 102 on rods ABC
Step 2: Subtract 7 from the tens rod B. Use the complement. Begin by subtracting 1 from hundreds rod A, then add the complementary 3 to rod B and so you are left with 32 on rods BC.
Step 3: Subtract 8 from units rod C. Use the complement again. Begin by subtracting 1 from hundreds rod A, then add the complementary 2 to rod C, leaving the answer 24 on rods BC.
Now, moving on to something that looks complicated but follows the same procedure for solving it.
146-57=89
Step 1: Set 146 on rods ABC.
Step 2: Subtract 5 from tens rod B. Use the complement. Begin by subtracting 1 from hundreds rod A, then add the complementary 5 to rod B, leaving 96 on rods ABC.
Step 3: Subtract 7 from units rod C. Use the complement again. Begin by subtracting 1 from hundreds rod A, then add the complement 3 to rod C, leaving the answer 89 on rods ABC.
22.3-2.8=19.5
Step 1: Designate rod B as the unit rod. Set 22.3 on rods ABC.
Step 2: Subtract 2 from units rod B, leaving 20.3 on rods ABC.
Step 3: Subtract 8 from tenths rod C. Use the complement. Begin by subtracting 1 from units rod on B but here seems to be a problem. Rod B is empty. There's nothing there to subtract, so you have to go all the way over to rod A for help.
Step 4: Subtract 1 from tens rod A. Add 9 to rod B, then add the complementary 2 to rod C, leaving 19.5 on rods ABC.
Though it might look as though the last example is a bit of stretch, but with practice, this can seem pretty easy.
If you want to try something complicated, you can start solving examples such as 78-102 or 2.8-22.3.
Basically, you need to start addressing negative numbers on an abacus.
Summary
The Abacus is the oldest counting equipment. From 5000 years ago to this 21st century, the abacus went through many transitions.
It started with a tray of sand and became a computerized calculating device. It is a huge journey but the sole purpose of the abacus remains the same, making the calculation easier.
Though Abacus is now replaced by electronic calculators and computers, as a mathematical teaching tool, its role is still intact.
Abacus is very useful and important for blind people, which is known as Cranmer Abacus.
Now that you know how to do subtraction using abacus, you can try more subtraction problems to strengthen your understanding.
To find out how the Cuemath program is different from the after-school abacus program, click here.
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Frequently Asked Questions (FAQs)
What is an Abacus?
An Abacus is a manual aid for calculating which consists of beads that can be moved up and down on a series of sticks or strings within a usually wooden frame. The Abacus itself doesn't calculate; it's merely a device for helping a human being calculate by remembering what has been counted.
Where was the Abacus invented?
The type of Abacus most commonly used today was invented in China around the 2nd century B.C. However, Abacus-like devices are first attested from ancient Mesopotamia around 2700 B.C.!
Where was Abacus first used?
The Abacus (plural abaci or abacuses), also called a counting frame, is a calculating tool used in the ancient Near East, Europe, China, and Russia, centuries before the adoption of the written Arabic numeral system. The exact origin of the Abacus is still unknown.
What are the advantages of learning how to use an Abacus?
Mathematical skills lay a secure foundation for higher classes.
Abacus education improves the skills of
- Visualization (photographic memory)
- Concentration
- Listening Skills
- Memory, Speed
- Accuracy
- Creativity
- Self Confidence
- Self-Reliance resulting in Whole Brain Development
Is it good for children to use an abacus?
Yes, an abacus is an excellent tool for teaching children basic math. The different senses involved in using an abacus, like sight and touch, can also reinforce the lessons
