Exercise 4: Add & Subtract 10–40
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In this exercise, you'll practice addition and subtraction using numbers 10 to 40 (multiples of 10). Each problem stays within 10–40, so you can solve it using your left hand only. Refresh or click "New Problem" to get a new question.
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Show the result on your left hand
💡 Tip: For subtraction, start from the larger number and "close" fingers one by one. For addition, start from the first number and "open" fingers for the second. Remember: left hand represents the tens place!
Learning Goals
- Fluency with finger positions for 10–40
- Mental calculation with tens without counting aloud
- Transition smoothly between operations
- Master the left hand for tens place
How It Works
1 Random problem generated (e.g.,
30 + 10, 40 – 30)2 You solve it mentally or with your left hand
3 Click "Show Answer" to verify — hand images appear