How To Add 2 and 3 Digit Numbers on an Abacus?
To add and subtract 2 and 3 digit numbers or even higher multi-digit numbers is the same as if we are working with single digit numbers. We use all the same techniques we learned in our basic skill training. We are now beginning to see the power of abacus math since although the numbers are increasing in size the complexity of solving each problem stays the same, one digit at a time.
Let’s take a look at solving the following problem.
| 896 |
| 769 |
| 36 |
| 697 |
| 68 |
First add 896 to the abacus.
Next we add 769 to 896 by first adding 7 to 8 on the 3rd rod using a 10 pair addition by adding 1 to the 4th rod and subtracting 3, the 10 pair of 7, from 8 on the 3rd rod. Then we add the 6 from 769 to the 9 on the 2nd rod using another 10 pair addition by adding 1 to 5 on the 3rd rod and subtracting 4, the 10 pair of 6, from 9 on the second rod. Finally we add the 9 of 769 to the 6 on the unit rod using a 10 pair addition by adding 1 to 5 on the 2nd rod and subtracting 1, the 10 pair of 9, from 6 on the unit rod for an interim sum of 1665.
Continuing we add 36 to the 1665 on the abacus by adding 3 to 6 on the 2nd rod resulting in 9. We are showing this simple addition first because it is setting up a multi-rod movement needed for adding the 6 of 36 to the 5 on the unit rod. Seeing that we have 9 on the second rod when we go to add the 6 to the 5 on the unit rod we will need to use two 10 pair additions to complete the movement, forward double rod. We will show this movement in the next graphic.
Now we add the 6 of 36 to the 5 on the unit rod using a 10 pair addition by first adding 1 to 9 on the 2nd rod. But however to add the 1 to 9 on the 2nd rod requires another 10 pair addition. For this second 10 pair addition we add 1 to 6 on the 3rd rod and subtract 9, the 10 pair of 1, from 9 on the 2nd rod. Now to complete the first 10 pair addition we subtract 4, the 10 pair of 6, from 5 on the unit rod using a 5 pair by adding 1 and subtracting 5. The resulting interim sum is now 1701.
Next we add 697 to 1701 on the abacus. First add 6 to 7 on the 3rd rod using a 10 pair addition by adding 1 to 2 on the 4th rod and subtracting 4, the 10 pair of 6, from 7 on the 3rd rod using a 5 pair adding 1 and subtracting 5. Next add 9 to 0 on the 2nd rod. Lastly add 7 to 1 on the unit rod for an interim sum of 2398.
To complete our addition problem we add 68 to 2398 by adding 6 to 9 on the 2nd rod using a 10 pair addition. First add 1 to 3 on the 3rd rod and subtract 4, the 10 pair of 6, from 9 on the 2nd rod. Lastly add 8 to 8 on the unit rod by adding 1 to 5 on the 2nd rod and subtracting 2, the 10 pair of 8, from 8 on the unit rod for a final answer of 2466.
