1. **Problem Statement:** Express the given ratios as percentages. 2. **Formula:** To convert a ratio $a:b$ to a percentage, use the formula: $$\text{Percentage} = \left(\frac{a}{b}\right) \times 100\%$$ 3. **Calculations:** (i) For $1:4$: $$\frac{1}{4} \times 100 = 25\%$$ (ii) For $2:7$: $$\frac{2}{7} \times 100 \approx 28.57\%$$ (iii) For $11:15$: $$\frac{11}{15} \times 100 \approx 73.33\%$$ (iv) For $25:12$: $$\frac{25}{12} \times 100 \approx 208.33\%$$ (v) For $18:45$: $$\frac{18}{45} \times 100 = 40\%$$ (vi) For $5:4$: $$\frac{5}{4} \times 100 = 125\%$$ 4. **Explanation:** We divide the first number by the second number in each ratio to get a decimal, then multiply by 100 to convert it to a percentage. **Final answers:** (i) 25% (ii) 28.57% (iii) 73.33% (iv) 208.33% (v) 40% (vi) 125%