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Addition

Level 12 / build-up

3d + 2d (ones carry)

4 visual steps / answer-window addition

1. Fill hundreds

Step 1: Fill hundreds
raw windows
running strip
Hundreds window: 4 + 0 = 4. Hold 4; wait for carry from the next window.

Hundreds window: 4 + 0 = 4. Hold 4; wait for carry from the next window.

2. Fill tens

Step 2: Fill tens
raw windows
running strip
Tens window: 3 + 2 = 5. Hold 5; wait for carry from the next window.

Tens window: 3 + 2 = 5. Hold 5; wait for carry from the next window.

3. Fill ones

Step 3: 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.

4. Settle carry

Step 4: Settle carry
Settle onceKeep ones; carry moves left.raw windows
settled digits
Settle raw 4 | 5 | 15 into 465; keep ones and move carry left.

Settle raw 4 | 5 | 15 into 465; keep ones and move carry left.

Practice Level 12

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

Start Level