1. 直接写出得数。
$\frac{1}{8}+\frac{3}{10}=$
$\frac{9}{20}+\frac{1}{5}=$
$\frac{1}{2}+\frac{3}{8}=$
$\frac{3}{13}+\frac{5}{26}=$
$\frac{7}{10}+\frac{8}{25}=$
$\frac{2}{11}+\frac{4}{33}=$
$\frac{1}{2}-\frac{5}{12}=$
$1-\frac{2}{13}=$
$\frac{1}{4}-\frac{1}{5}=$
$2-1\frac{3}{8}=$
$\frac{4}{3}-\frac{2}{9}=$
$\frac{17}{24}-\frac{1}{3}=$
$3.3×\frac{1}{3}=$
$\frac{5}{9}×\frac{4}{5}=$
$\frac{8}{11}×\frac{11}{8}=$
$0.36×\frac{5}{6}=$
$5.5×\frac{4}{55}=$
$\frac{1}{6}×\frac{5}{6}=$
$\frac{3}{8}÷6=$
$\frac{15}{16}÷\frac{1}{8}=$
$5÷\frac{1}{5}=$
$\frac{30}{13}÷\frac{15}{13}=$
$\frac{7}{32}÷\frac{7}{16}=$
$\frac{15}{14}÷\frac{15}{7}=$
实际用了：分钟

1. $\frac{17}{40}\quad \frac{1}{12}\quad \frac{11}{10}\quad \frac{1}{16}$
$\frac{13}{20}\quad \frac{11}{13}\quad \frac{4}{9}\quad \frac{15}{2}$
$\frac{7}{8}\quad \frac{1}{20}\quad 1\quad 25$
$\frac{11}{26}\quad \frac{5}{8}\quad \frac{3}{10}\quad 2$
$\frac{51}{50}\quad \frac{10}{9}\quad \frac{2}{5}\quad \frac{1}{2}$
$\frac{10}{33}\quad \frac{3}{8}\quad \frac{5}{36}\quad \frac{1}{2}$

2. 计算下面各题。
$\frac{7}{4}×\frac{5}{8}+\frac{1}{4}÷\frac{8}{5}$
$(\frac{2}{3}+\frac{1}{5})÷\frac{13}{30}-\frac{1}{2}$
$\frac{11}{20}÷(\frac{4}{9}+\frac{1}{6})×\frac{5}{27}$

2. $\frac{5}{4}\quad \frac{3}{2}\quad \frac{1}{6}$

3. 下面哪组中的两个比可以组成比例？把组成的比例写出来。
(1) $\frac{3}{10}:\frac{9}{20}$和$\frac{5}{6}:\frac{15}{14}$
(2) $25:20$和$10:8$

3. (1)不能
(2)$25:20=10:8$

计算: $( \frac{1}{2} + \frac{1}{3} + \frac{1}{4} + \frac{1}{5} ) × ( \frac{1}{3} + \frac{1}{4} + \frac{1}{5} + \frac{1}{6} ) - ( \frac{1}{2} + \frac{1}{3} + \frac{1}{4} + \frac{1}{5} + \frac{1}{6} ) × ( \frac{1}{3} + \frac{1}{4} + \frac{1}{5} )$

$\frac{1}{12}$