AbacusMinds

Lesson 12: Advanced Abacus Calculations

Combine every technique: long chains, three-digit numbers, two-digit multipliers and decimals.

Advanced 30 minutes Lesson 12 of 12

Long chains

Advanced learners add 5–10 three-digit numbers in a row. The technique is exactly what you already know, applied rod by rod from left to right.

Example: 456 + 278 − 129. 456 + 278 = 734, then 734 − 129 = 605.

456 + 278 − 129 = 605

Combination moves

Some steps need a big friend and a small friend together. For 5 + 7: we must add 10 and take away 3, but the ones rod shows only the heaven bead. Taking away 3 needs a small friend: −5 +2. So the full move is +10, −5, +2, giving 12.

Two-digit × two-digit

Example: 34 × 26. Break it into four partial products and add each one:

  • 30 × 20 = 600
  • 30 × 6 = 180 → 780
  • 4 × 20 = 80 → 860
  • 4 × 6 = 24 → 884

Decimals

Choose a unit rod with a dot. Rods to its right are tenths, hundredths and so on. 3.75 is 3 on the unit rod, 7 on the next rod right and 5 on the one after. Add and subtract decimals exactly like whole numbers. Just keep the unit rod fixed.

You have finished the course! Keep your skills sharp with daily practice on the practice page and the Level 3 worksheets.

Try it yourself

Work out 34 × 26 using partial products and show the answer.

Your abacus shows 0.

Quick check

Type your answers, then check them. Get them all right to complete the lesson automatically.

Practice tips

  • For long chains, keep a steady rhythm rather than rushing single numbers.
  • Mix abacus work with anzan: do a chain on the abacus, then the same chain in your head.