AbacusMinds

Lesson 9: Two-Digit Subtraction

Subtract two-digit numbers left to right, borrowing from the next rod with big friends.

Intermediate 20 minutes Lesson 9 of 12

Without borrowing

Example: 68 − 23. Set 68. Take 2 from the tens rod (→ 48). Take 3 from the ones rod (→ 45).

With borrowing

Example: 52 − 27.

  1. Set 52.
  2. Tens: take away 2 → 32.
  3. Ones: take away 7. The ones rod only has 2, so use a big friend: take 1 from the tens rod (−10) and add 3 to the ones rod → 25.
Start: 52
−20
−7 (−10, +3) → 25
Check: 25 + 27 = 52. Adding back is the fastest way to catch mistakes.

Mixed chains

Once you are confident, try chains that mix adding and subtracting, like 45 + 32 − 18. Work one number at a time and never clear the abacus in the middle.

Try it yourself

Show 52, then take away 27: tens first, then ones.

Your abacus shows 0.

Quick check

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

Practice tips

  • If you borrow, the tens rod drops by one extra. Watch for it.
  • Mixed chains are where real abacus speed comes from. Do a few every day.