1. 直接写出得数。
$\frac{3}{7}+\frac{1}{4}=$ $\frac{3}{2}-\frac{2}{3}=$ $\frac{4}{15}+\frac{4}{9}=$ $\frac{4}{5}-\frac{3}{10}+\frac{3}{20}=$
$49×\frac{3}{7}=$ $25×\frac{1}{15}=$ $12×\frac{9}{20}=$ $45×\frac{7}{9}×\frac{5}{7}=$
$\frac{4}{5}×\frac{55}{56}=$ $\frac{8}{9}×\frac{9}{8}=$ $\frac{7}{36}×\frac{72}{35}=$ $\frac{4}{3}×\frac{9}{14}×\frac{7}{2}=$
$\frac{5}{6}×\frac{12}{25}=$ $\frac{7}{4}×\frac{8}{21}=$ $\frac{9}{22}×\frac{11}{6}=$ $\frac{5}{18}×\frac{27}{10}×3=$
$\frac{30}{7}×\frac{7}{6}=$ $\frac{6}{7}×\frac{3}{14}=$ $\frac{3}{7}×\frac{14}{15}=$ $\frac{21}{26}×\frac{13}{14}×\frac{16}{9}=$
$\frac{3}{4}×64=$ $\frac{5}{24}×\frac{4}{7}=$ $\frac{7}{12}×\frac{1}{42}=$ $\frac{12}{35}×\frac{7}{20}×\frac{20}{7}=$

1. $\frac{19}{28}$ $\frac{5}{6}$ $\frac{32}{45}$ $\frac{13}{20}$
21 $\frac{5}{3}$ $\frac{27}{5}$ 25
$\frac{11}{14}$ 1 $\frac{2}{5}$ 3
$\frac{2}{5}$ $\frac{2}{3}$ $\frac{3}{4}$ $\frac{9}{4}$
5 $\frac{9}{49}$ $\frac{2}{5}$ $\frac{4}{3}$
48 $\frac{5}{42}$ $\frac{1}{72}$ $\frac{12}{35}$

2. 计算下面各题。
$\frac{8}{15}×35×\frac{3}{14}$ $\frac{16}{39}×\frac{26}{27}×\frac{9}{16}$ $\frac{9}{32}×\frac{22}{17}×\frac{16}{99}$
$\frac{5}{2}×\frac{4}{5}×8$ $\frac{3}{8}×\frac{5}{6}×\frac{8}{15}$ $\frac{13}{24}×\frac{3}{13}×\frac{5}{6}$

2. 4 $\frac{2}{9}$ $\frac{1}{17}$
16 $\frac{1}{6}$ $\frac{5}{48}$

比较$\frac{4443}{5554}$、$\frac{5557}{6668}$和$\frac{6668}{7779}$这三个分数的大小。