1. Direct addition
When there are enough free beads on the rod, simply push them to the beam.
Example: 2 + 1 = 3. Show 2, push up one more earth bead. Done.
Example: 3 + 5 = 8. Show 3, bring the heaven bead down.
2. Small friends – pairs that make 5
Sometimes there are not enough earth beads left. Then we use a small friend: two numbers that add up to 5.
| Number | 1 | 2 | 3 | 4 |
|---|---|---|---|---|
| Small friend | 4 | 3 | 2 | 1 |
Example: 4 + 3 = 7. All four earth beads are up, so we cannot push up three more. Add 5 (heaven bead down) and take away 2 (the small friend of 3). The rod now shows 7.
3. Big friends – pairs that make 10
When a rod cannot hold the answer, we carry to the next rod on the left using a big friend: two numbers that add up to 10.
| Number | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 |
|---|---|---|---|---|---|---|---|---|---|
| Big friend | 9 | 8 | 7 | 6 | 5 | 4 | 3 | 2 | 1 |
Example: 8 + 5 = 13. The ones rod shows 8. Take away 5 (the big friend of 5) to leave 3, then add 1 on the tens rod. Answer: 13.
Try it yourself
Start from 0. Show 8, then add 5 using big friends. Stop when the abacus shows the answer.
Quick check
Type your answers, then check them. Get them all right to complete the lesson automatically.
Practice tips
- Learn the small friend and big friend pairs by heart. Every later lesson depends on them.
- Always work the abacus in the same order: add on the left rod before you take away on the right.