Exercise 3: Mastering Numbers 1-9
Ready for the full challenge! In this exercise, you'll work with all numbers from 1 to 9. All operands are between 1-9, and intermediate results stay within 0-9, using your right hand only.
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Show the result on your right hand
Conversion Technique: Thumb and Other Fingers
Basic Rules:
- Extended finger = counting
- Bent finger = not counting
- 4 fingers (index, middle, ring, pinky) = 1 each
- Thumb = 5
Key Principles:
- When thumb is extended and want to subtract one → thumb bends, 4 other fingers extend
- When 4 fingers are extended and want to add one → thumb extends, 4 other fingers bend
Example: 2 + 3 = 5
Step 1: Extend 2 fingers (index + middle) = 2
Step 2: Add 3 means need to extend 3 more fingers
- Extend ring finger = 3
- Extend pinky = 4
- Out of fingers! Need 1 more finger
Step 3: Conversion
- Bend all 4 fingers
- Extend thumb → 5!
Explanation: 2 + 3 = 5 is actually 2 + 2 = 4, then 4 + 1 = 5 (convert 4 fingers to thumb)
Example: 5 - 2 = 3
Step 1: Extend thumb = 5
Step 2: Subtract 2 means need to reduce by 2 units
- Need to subtract 1 first: Bend thumb
- But no other fingers extended to bend!
Step 3: Conversion
- Bend thumb
- Extend all 4 fingers = 4
- Continue subtracting:
4 - 1 = 3→ Bend pinky
Result: 3 fingers extended (index + middle + ring) = 3
Explanation: 5 - 2 = 3 is actually 5 - 1 = 4 (convert thumb to 4 fingers), then 4 - 1 = 3
Quick Conversion Reference:
| Calculation | Action |
|---|---|
4 + 1 = 5 | Bend 4 fingers → extend thumb |
5 - 1 = 4 | Bend thumb → extend 4 fingers |
3 + 2 = 5 | Extend 1 more (= 4), then convert to 5 |
2 + 3 = 5 | Extend 2 more (= 4), then convert to 5 |
5 - 2 = 3 | Convert to 4, then bend 1 finger |
Complement Patterns Across 5
When adding or subtracting with the right hand thumb, observe these patterns:
Addition Patterns:
- Right hand: +4 = +5 -1
- Right hand: +3 = +5 -2
- Right hand: +2 = +5 -3
- Right hand: +1 = +5 -4
Subtraction Patterns:
- Right hand: -4 = -5 +1
- Right hand: -3 = -5 +2
- Right hand: -2 = -5 +3
- Right hand: -1 = -5 +4
⚠️ Important: Start by counting each step individually. Only apply these mental shortcuts once you've become thoroughly familiar with the basic movements!
💡 Tip: For 6-9, remember you're using both your thumb (5) and fingers (1-4). For example: 7 = thumb + 2 fingers. Practice converting back and forth between representations!
Learning Goals
- Master all numbers 1-9 on right hand
- Fluent transitions through 5 boundary
- Handle multi-step calculations smoothly
- Build speed and accuracy
Key Concept
Right Hand Values:
- Thumb = 5
- Each finger = 1
- 6 = Thumb + 1 finger
- 7 = Thumb + 2 fingers
- 8 = Thumb + 3 fingers
- 9 = Thumb + 4 fingers
Remember: Numbers 6-9 always have the thumb extended plus 1-4 fingers.