Abacus Level 3: Combination

What you’ll learn

• When to use both friends in one move
• The 8 combination formulas
• 2- and 3-digit sums with 3–5 rows

Combination formulas

• +6 = +1 −5 +10
• +7 = +2 −5 +10
• +8 = +3 −5 +10
• +9 = +4 −5 +10
• −6 = −10 +5 −1
• −7 = −10 +5 −2
• −8 = −10 +5 −3
• −9 = −10 +5 −4

▶ Watch it on the abacus

6 + 7 = 13: +7 = +2 −5 +10 → 8, 3, then 13.

✏️ Practice

Work the sum on the abacus and press Check (or type the answer). Stuck? “Show me how”.

🏁 Level 3 test

20 sums. Work each sum on the abacus, press Check, then go to the next one. Get 16 or more right to pass the level.

🎓 Sign in with Google to get a certificate and the 🎯 Combo Champion badge when you pass. You can still take the test without signing in.

🖨️ Level 3 worksheets

• Worksheet set 1
• Worksheet set 2
• Worksheet set 3