How do we actually perform addition? There are 3 techniques which must be mastered in order to add any series of numbers (Simple, Best Friend, and Second Friend).
Technique 1 - Simple Addition
The Problem: How do we solve 2 + 2?
Using the 1’s beads, move 2 beads up toward the white bar.
Now we want to add 2 more.
Since there are 2 free 1’s beads, we can just push them up.
As we can see, the answer is 4.
Technique 2 - Friends to 10
The Problem: How do we solve 2 + 9?
Start by placing 2 on the Soroban.
Now we want to add 9 more.
Looking at the unused beads on the Soroban, there is one 5-bead, and two 1-beads, for a total of 7. Since we do NOT have 9 more to add, we challenge our kids to ask “What else can I do?”
We teach our students to use the TENS column.
Tens Ones
So, instead of adding 9 (which is impossible), we add 10 instead.
But, 10 is 1 more than 9, so we have to take 1 away.
As we can see, the answer is 11.
Technique 3 - Friends to 5
The Problem: How do we solve 2 + 4?
Start by placing 2 on the Soroban.
Now we want to add 4 more.
Looking at the unused beads on the Soroban, there is one 5-bead, and two 1-beads, for a total of 7. Since we cannot make a 4 out of the available beads, we challenge our kids to ask “What else can I do?”
The first inclination is to use the previous technique, Friends to 10.
The student adds 10, and because 10 is 6 more than 4, we attempt to take 6 away from the Ones place. But we encounter another problem, we only have 2, so how can we take away 6??????
Once again, our students are challenged to ask themselves “What else can I do?”
So, instead of adding 4 (which is impossible), and instead of adding 10 (which we reasoned was a dead end), we add 5 instead.
But 5 is 1 more than 4, so we have to take 1 away.
As we can see, the answer is 6.