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Addition

Level 22 / mastery

4d + 3d (ones carry)

5 visual steps / large answer-window addition

1. Fill thousands

Step 1: Fill thousands
raw windows
running strip
Thousands window: 3 + 0 = 3. Hold 3; wait for carry from the next window.

Thousands window: 3 + 0 = 3. Hold 3; wait for carry from the next window.

2. Fill hundreds

Step 2: Fill hundreds
raw windows
running strip
Hundreds window: 6 + 2 = 8. Hold 8; wait for carry from the next window.

Hundreds window: 6 + 2 = 8. Hold 8; wait for carry from the next window.

3. Fill tens

Step 3: Fill tens
raw windows
running strip
Tens window: 4 + 5 = 9. Hold 9; wait for carry from the next window.

Tens window: 4 + 5 = 9. Hold 9; wait for carry from the next window.

4. Fill ones

Step 4: Fill ones
raw windows
running strip
Ones window: 8 + 7 = 15. Hold raw 15; settle carry later.

Ones window: 8 + 7 = 15. Hold raw 15; settle carry later.

5. Settle carry

Step 5: Settle carry
Settle onceKeep ones; carry moves left.raw windows
settled digits
Settle raw 3 | 8 | 9 | 15 into 3905; keep ones and move carry left.

Settle raw 3 | 8 | 9 | 15 into 3905; keep ones and move carry left.

Practice Level 22

A few quick rounds make digit release automatic; carry is the only thing to keep.

Start Level