1. 直接写出得数。
0.8 + 2.6 =
7.2 ÷ 0.8 =
4.56 + 0.2 =
4.3 × 0.2 + 0.8 =
1.1 ÷ 100 =
100 - 27 =
4 ÷ 0.25 =
6.3 ÷ 3 × 0.1 =
3.2 × 0.6 =
5.4 ÷ 0.09 =
3.2 ÷ 0.04 =
7.58 + 0.52 - 0.1 =
602 - 512 =
4.4 ÷ 1.1 =
1 - 0.01 =
6.5 ÷ 0.13 × 0.01 =
$\frac{7}{15} + \frac{2}{5} =$
0.8 × $\frac{3}{8} =$
$\frac{15}{19} × \frac{7}{3} =$
14 × $\frac{2}{7} - 3 =$
$\frac{3}{5} ÷ 0.1 =$
$\frac{1}{12} + \frac{2}{3} =$
$\frac{2}{3} + \frac{2}{21} =$
$\frac{1}{9} + \frac{1}{5} + \frac{8}{9} =$
$\frac{3}{5} × \frac{2}{5} =$
$\frac{4}{15} - \frac{2}{9} =$
$\frac{1}{12} × \frac{16}{9} =$
$1 - \frac{4}{5} × \frac{10}{9} =$
$1 ÷ \frac{20}{33} =$
$15 ÷ \frac{9}{8} =$
$\frac{4}{15} ÷ 1.6 =$
$\frac{7}{8} ÷ (1 - \frac{7}{8}) =$

0.8 + 2.6 = 3.4
7.2 ÷ 0.8 = 9
4.56 + 0.2 = 4.76
4.3 × 0.2 + 0.8 = 1.66
1.1 ÷ 100 = 0.011
100 - 27 = 73
4 ÷ 0.25 = 16
6.3 ÷ 3 × 0.1 = 0.21
3.2 × 0.6 = 1.92
5.4 ÷ 0.09 = 60
3.2 ÷ 0.04 = 80
7.58 + 0.52 - 0.1 = 8
602 - 512 = 90
4.4 ÷ 1.1 = 4
1 - 0.01 = 0.99
6.5 ÷ 0.13 × 0.01 = 0.5
$\frac{7}{15} + \frac{2}{5} = \frac{13}{15}$
0.8 × $\frac{3}{8} = 0.3$
$\frac{15}{19} × \frac{7}{3} = \frac{35}{19}$
14 × $\frac{2}{7} - 3 = 1$
$\frac{3}{5} ÷ 0.1 = 6$
$\frac{1}{12} + \frac{2}{3} = \frac{3}{4}$
$\frac{2}{3} + \frac{2}{21} = \frac{16}{21}$
$\frac{1}{9} + \frac{1}{5} + \frac{8}{9} = 1\frac{1}{5}$
$\frac{3}{5} × \frac{2}{5} = \frac{6}{25}$
$\frac{4}{15} - \frac{2}{9} = \frac{2}{45}$
$\frac{1}{12} × \frac{16}{9} = \frac{4}{27}$
$1 - \frac{4}{5} × \frac{10}{9} = \frac{1}{9}$
$1 ÷ \frac{20}{33} = \frac{33}{20}$
$15 ÷ \frac{9}{8} = \frac{40}{3}$
$\frac{4}{15} ÷ 1.6 = \frac{1}{6}$
$\frac{7}{8} ÷ (1 - \frac{7}{8}) = 7$

2. 用竖式计算，带☆的要验算。
0.285÷0.38=
0.85×24.5≈
（得数保留两位小数）
7.42÷1.2≈
（得数保留两位小数）
5.4×23=
☆12.6÷0.28=
6.15×0.36=

0.285÷0.38=0.75
0.85×24.5≈20.83
7.42÷1.2≈6.18
5.4×23=124.2
☆12.6÷0.28=45
6.15×0.36=2.214
竖式及验算略

整数、分数和小数的除法的算理是一致的，如果被除数和除数的计数单位相同，可以直接用计数单位的个数相除。请你根据这一方法计算0.4÷0.02。

0.4÷0.02=0.40÷0.02=(0.01×40)÷(0.01×2)=40÷2=20