1. **State the problem:** Rose needs 200 litres of water to make 5 litres of iced tea. We want to find out how much water she needs to make 300 ml (which is 0.3 litres) of iced tea. 2. **Set up the proportion:** Since the amount of water is proportional to the amount of iced tea, we use the formula: $$\frac{\text{water}_1}{\text{tea}_1} = \frac{\text{water}_2}{\text{tea}_2}$$ where $\text{water}_1 = 200$ litres, $\text{tea}_1 = 5$ litres, $\text{tea}_2 = 0.3$ litres, and $\text{water}_2$ is what we want to find. 3. **Write the equation:** $$\frac{200}{5} = \frac{\text{water}_2}{0.3}$$ 4. **Solve for $\text{water}_2$:** Multiply both sides by 0.3: $$\text{water}_2 = \frac{200}{5} \times 0.3$$ 5. **Simplify the fraction:** $$\text{water}_2 = \cancel{\frac{200}{5}} \times 0.3 = 40 \times 0.3$$ 6. **Calculate the result:** $$\text{water}_2 = 12$$ litres **Answer:** Rose needs 12 litres of water to make 300 ml of iced tea.