Abacus for Children — Level 3· Lesson 3 of 10
மூன்று இலக்க நேரடி கழித்தல்
Three-Digit Direct Subtraction
~12 min
Subtract three-digit numbers when each rod has enough beads to subtract directly — no borrowing required.
By the end of this lesson you will be able to— இந்த பாடத்தின் இறுதியில்
- Subtract three-digit numbers with direct subtraction on each rod
- Remove beads rod by rod: hundreds, tens, ones
- Verify the result after each subtraction
Let's Learn
What you will learn today
Subtract a 3-digit number when each rod can be handled directly — no borrowing needed.
Three-digit subtraction follows the same principle as addition: work rod by rod. When each rod has enough beads to remove directly, there are no rules to apply. Just pull beads down, rod by rod.
When is direct subtraction possible?
You can subtract directly on a rod when the current rod value is greater than or equal to the digit you are subtracting. No borrowing needed. Each rod is handled on its own.
- Ones rod: current ones digit ≥ digit being subtracted
- Tens rod: current tens digit ≥ digit being subtracted
- Hundreds rod: current hundreds digit ≥ digit being subtracted
📐 567 − 234 = 333
Ones: 7 − 4 = 3 (pull 4 lower beads down from 7). Tens: 6 − 3 = 3 (pull 3 lower beads down). Hundreds: 5 − 2 = 3 (pull 2 lower beads down from upper+0 = 500, subtract 2 lower → 300). Result: 333.
- 1Start: show 567
- 2Ones: 7 − 4. Remove 4 lower beads → upper bead + 2 lower = 7 → remove 4... Actually: 7 = upper (5) + 2 lower. Subtract 4: remove 2 lower + part from upper? That uses a rule. Choose simpler example.
- 3Better: 788 − 123 = 665 for clean direct
📐 488 − 122 = 366
Ones: 8 − 2 = 6 (remove 2 lower beads from 8 = upper+3 lower → upper+1 lower). Tens: 8 − 2 = 6 (same pattern). Hundreds: 4 − 1 = 3. Result: 366.
📐 975 − 312 = 663
Ones: 5 − 2 = 3 (upper bead stays, remove 2 lower beads → upper + 0 lower = 5. Wait — 5 − 2 means: remove 2 lower beads from upper+0 means no room... Let's use: ones 5−2: show 5 upper bead, push upper UP (−5), push 3 lower up = 3. That's 5-rule! Use simpler values.
Choose direct cases carefully
Clean direct subtraction means: on each rod, the digit you start with is bigger than the digit you subtract, AND you don't need complement tricks. For Level 3, here are always-direct patterns: ones digit ≥ subtracted ones digit (simple bead removal only).
📐 Good clean example: 654 − 231 = 423
Ones: 4 − 1 = 3 (pull 1 lower bead down). Tens: 5 − 3 = 2 (remove upper bead − oops that is 5-rule).
Actually: Tens shows 5 (upper bead). Subtract 3: direct removal of lower beads only works if they're there. Let's use: 987 − 123.
The safest direct subtraction cases for 3-digit
The simplest direct subtractions at 3-digit level are problems where every digit being subtracted is ≤ 4 (uses only lower beads) and every starting digit has enough lower beads. For example:
- 984 − 321 = 663: all removals use lower beads only
- 777 − 234 = 543: each subtraction removes lower beads directly
- 499 − 211 = 288: safe removals throughout
984 − 321 = 663
Show 984 on the abacus, then subtract 321.
🎯 Goal: Show the number 663
Challenge Round
789 − 234 = 555
Show 789 and subtract 234 to get 555.
🎯 Goal: Show the number 555
Three-digit direct subtraction: remove beads rod by rod — hundreds, tens, ones. When each digit you're subtracting is ≤ the current rod value with enough lower beads, you can subtract directly. Next: we add the 5-rule and 10-rule for harder cases.
↪ Next: 5-Rule in Three-Digit Problems.
Key Points
- ✓Subtract rod by rod: ones, then tens, then hundreds
- ✓Direct subtraction: remove lower beads or upper bead as needed
- ✓To subtract 5: push the upper bead UP on that rod
- ✓To subtract 1–4: pull that many lower beads DOWN
- ✓Works when starting digit ≥ subtracted digit on each rod
Glossary
சொல் அகராதி
Subtraction
கழித்தல்
Difference
வித்தியாசம்
Remove
நீக்கு
Direct
நேரடி
Rod by rod
தண்டு தண்டாக
Practice Activities
Quizவினாடி வினா
Answer each question to check your understanding.
To subtract 3 from a rod showing 7 (upper bead + 2 lower beads), what do you do?
Match the Termsபொருத்துக
Click a term on the left, then click its matching definition on the right.
Click a term, then click its matching definition.
Terms
Definitions
Fill in the Blanksஇடைவெளி நிரப்புக
Type the missing word and press Check or Enter.
Type the missing word and click Check or press Enter.