1. **Problem:** Mr. Jonas made a scale drawing with scale 1 cm : 3 m. The actual length is 12 m. Find the length on the drawing. 2. **Formula:** Scale drawing length = Actual length \div Scale factor 3. **Calculation:** $$\text{Length on drawing} = \frac{12}{3} = 4 \text{ cm}$$ 4. **Answer:** The length of the addition on the drawing is 4 cm.