الف) \( 8 \div 0.2 = 8 \times 5 = 40 \).
ب) \( 0.81 \div 0.9 = \frac{81}{100} \div \frac{9}{10} = \frac{81}{100} \times \frac{10}{9} = \frac{81 \times 10}{100 \times 9} = \frac{810}{900} = \frac{9}{10} = 0.9 \).
ج) \( 0.025 \div 0.05 = \frac{25}{1000} \div \frac{5}{100} = \frac{25}{1000} \times \frac{100}{5} = \frac{25 \times 100}{1000 \times 5} = \frac{2500}{5000} = \frac{1}{2} = 0.5 \).