1. 直接写出得数。
$5 ÷ \frac{3}{5} =$
$6 ÷ \frac{1}{4} =$
$12 ÷ \frac{8}{7} =$
$7 ÷ \frac{14}{15} =$
$\frac{2}{3} ÷ \frac{4}{5} =$
$\frac{7}{8} ÷ \frac{7}{12} =$
$\frac{3}{5} ÷ \frac{8}{15} =$
$\frac{1}{4} ÷ \frac{4}{15} =$
$\frac{9}{16} ÷ 3 =$
$\frac{15}{41} ÷ 5 =$
$\frac{12}{19} ÷ 16 =$
$\frac{3}{8} ÷ 6 =$
$24 ÷ \frac{12}{17} =$
$20 ÷ \frac{10}{11} =$
$\frac{12}{19} ÷ 8 =$
$60 ÷ \frac{1}{2} =$

$5 ÷ \frac{3}{5} = \frac{25}{3}$
$6 ÷ \frac{1}{4} = 24$
$12 ÷ \frac{8}{7} = \frac{21}{2}$
$7 ÷ \frac{14}{15} = \frac{15}{2}$
$\frac{2}{3} ÷ \frac{4}{5} = \frac{5}{6}$
$\frac{7}{8} ÷ \frac{7}{12} = \frac{3}{2}$
$\frac{3}{5} ÷ \frac{8}{15} = \frac{9}{8}$
$\frac{1}{4} ÷ \frac{4}{15} = \frac{15}{16}$
$\frac{9}{16} ÷ 3 = \frac{3}{16}$
$\frac{15}{41} ÷ 5 = \frac{3}{41}$
$\frac{12}{19} ÷ 16 = \frac{3}{76}$
$\frac{3}{8} ÷ 6 = \frac{1}{16}$
$24 ÷ \frac{12}{17} = 34$
$20 ÷ \frac{10}{11} = 22$
$\frac{12}{19} ÷ 8 = \frac{3}{76}$
$60 ÷ \frac{1}{2} = 120$

2. 在○里填上 “＞”“＜” 或 “=”。
$\frac{13}{11} × \frac{6}{7} ◯ \frac{6}{7}$
$\frac{4}{9} ÷ \frac{7}{5} ◯ \frac{4}{9}$
$\frac{2}{3} × \frac{1}{4} ◯ \frac{2}{3} ÷ 4$
$\frac{4}{5} ◯ \frac{8}{5} ÷ \frac{2}{3}$
$\frac{5}{8} ÷ \frac{1}{2} ◯ \frac{5}{8} × \frac{1}{2}$
$\frac{9}{15} × \frac{5}{3} ◯ \frac{9}{15} ÷ \frac{5}{3}$

$\frac{13}{11} × \frac{6}{7} ＞ \frac{6}{7}$
$\frac{4}{9} ÷ \frac{7}{5} ＜ \frac{4}{9}$
$\frac{2}{3} × \frac{1}{4} = \frac{2}{3} ÷ 4$
$\frac{4}{5} ＜ \frac{8}{5} ÷ \frac{2}{3}$
$\frac{5}{8} ÷ \frac{1}{2} ＞ \frac{5}{8} × \frac{1}{2}$
$\frac{9}{15} × \frac{5}{3} ＞ \frac{9}{15} ÷ \frac{5}{3}$

3. 计算下面各题。
$\frac{3}{11} + \frac{1}{12} ÷ \frac{1}{9} + \frac{1}{4}$
$0.25 × \frac{9}{13} ÷ \frac{1}{4}$
$\frac{7}{9} ÷ \frac{2}{3} ÷ \frac{14}{9}$

$\frac{3}{11} + \frac{1}{12} ÷ \frac{1}{9} + \frac{1}{4}$
$= \frac{3}{11} + \frac{1}{12} × 9 + \frac{1}{4}$
$= \frac{3}{11} + \frac{3}{4} + \frac{1}{4}$
$= \frac{3}{11} + (\frac{3}{4} + \frac{1}{4})$
$= \frac{3}{11} + 1$
$= 1\frac{3}{11}$
$0.25 × \frac{9}{13} ÷ \frac{1}{4}$
$= \frac{1}{4} × \frac{9}{13} × 4$
$= \frac{1}{4} × 4 × \frac{9}{13}$
$= 1 × \frac{9}{13}$
$= \frac{9}{13}$
$\frac{7}{9} ÷ \frac{2}{3} ÷ \frac{14}{9}$
$= \frac{7}{9} × \frac{3}{2} × \frac{9}{14}$
$= \frac{7}{9} × \frac{9}{14} × \frac{3}{2}$
$= \frac{1}{2} × \frac{3}{2}$
$= \frac{3}{4}$

要将20 g盐分两次溶入一杯水中，第一次加入盐后，盐的质量占盐水质量的$\frac{1}{10}$。第二次加入剩下的盐后，盐的质量占盐水质量的$\frac{2}{11}$。第一次加入了多少克盐？
反思 我错了（）道题。
自我评价：

$\begin{aligned}20÷\frac{2}{11-2}&=90\ (\mathrm{g})\\90÷\frac{10-1}{10}&=100\ (\mathrm{g})\\100-90&=10\ (\mathrm{g})\end{aligned}$
答：第一次加入了10克盐。