1. Problem: Convert 4 m² to dm². 2. Formula: To convert square meters to square decimeters, use the conversion factor $1\text{ m} = 10\text{ dm}$, so $1\text{ m}^2 = 10^2 = 100\text{ dm}^2$. 3. Calculation: Multiply the area in m² by 100 to get dm². $$4\text{ m}^2 \times 100 = 400\text{ dm}^2$$ 4. Explanation: Since 1 meter equals 10 decimeters, the area conversion involves squaring the linear conversion factor, resulting in multiplying by 100. Final answer: $4\text{ m}^2 = 400\text{ dm}^2$.