Ôn tập: Phép nhân và phép chia hai phân số

$\frac{3}{10}x\frac{4}{9}\mathit{=}\frac{\mathit{3}\mathit{x}\mathit{4}}{\mathit{10}\mathit{x}\mathit{9}}\mathit{=}\frac{\mathit{2}}{\mathit{5}\mathit{x}\mathit{3}}\mathit{=}\frac{\mathit{2}}{\mathit{15}}$

$\frac{6}{5}:\frac{3}{7}=\frac{6\mathrm{x}7}{5\mathrm{x}3}=\frac{2\mathrm{x}7}{5}=\frac{14}{5}$

$\frac{3}{4}\mathrm{x}\frac{2}{5}=\frac{3\mathrm{x}2}{4\mathrm{x}5}=\frac{3}{2\mathrm{x}5}=\frac{3}{10}$

$\frac{5}{8}:\frac{1}{2}=\frac{5\mathrm{x}2}{8\mathrm{x}1}=\frac{5}{4}$

$4\mathrm{x}\frac{3}{8}=\frac{4\mathrm{x}3}{8}=\frac{3}{2}$

$3:\frac{1}{2}=3\mathrm{x}2=6$

$\frac{1}{2}:3=\frac{1}{2\mathrm{x}3}=\frac{1}{6}$

$\frac{9}{10}x\frac{5}{6}\mathit{=}\frac{\mathit{9}\mathit{x}\mathit{5}}{\mathit{10}\mathit{x}\mathit{6}}\mathit{=}\frac{\mathit{3}\mathit{x}\mathit{3}\mathit{x}\mathit{5}}{\mathit{2}\mathit{x}\mathit{5}\mathit{x}\mathit{2}\mathit{x}\mathit{3}}\mathit{=}\frac{\mathit{3}}{\mathit{2}\mathit{x}\mathit{2}}\mathit{=}\frac{\mathit{3}}{\mathit{4}}$

$\frac{6}{25}:\frac{21}{20}=\frac{6\mathrm{x}20}{25\mathrm{x}21}=\frac{2\mathrm{x}3\mathrm{x}5\mathrm{x}4}{5\mathrm{x}5\mathrm{x}3\mathrm{x}7}=\frac{8}{35}$

$\frac{40}{7}\mathrm{x}\frac{14}{5}=\frac{40\mathrm{x}14}{7\mathrm{x}5}=\frac{8\mathrm{x}5\mathrm{x}7\mathrm{x}2}{7\mathrm{x}5}=8\mathrm{x}2=16$

$\frac{17}{13}:\frac{51}{26}=\frac{17\mathrm{x}26}{13\mathrm{x}51}=\frac{17\mathrm{x}13\mathrm{x}2}{13\mathrm{x}17\mathrm{x}3}=\frac{2}{3}$

Diện tích tấm bìa là:

Diện tích mỗi phần là: