一、口算。
$640÷20=$
$210×30=$
$20×0.9=$
$1110-111=$
$2500÷125=$
$1.25×0.008=$
$2.5×0.08=$
$1.24+9.8=$
$12-3.1=$
$293+260=$
$0.75÷0.05=$
$32÷0.5=$
$3.2-1.6=$
$3.6+0.12=$
$40×60=$
$\frac{8}{15}÷\frac{8}{3}=$
$\frac{3}{8}-\frac{1}{6}=$
$\frac{1}{3}+\frac{5}{6}=$
$\frac{1}{2}÷\frac{3}{4}=$
$\frac{5}{9}÷\frac{2}{3}=$
$\frac{5}{12}+\frac{1}{4}=$
$125×\frac{4}{25}=$
$\frac{5}{12}÷\frac{5}{8}=$
$\frac{3}{8}÷\frac{5}{32}=$

32
6300
18
999
20
0.01
0.2
11.04
8.9
553
15
64
1.6
3.72
2400
$\frac{1}{5}$
$\frac{5}{24}$
$\frac{7}{6}$
$\frac{2}{3}$
$\frac{5}{6}$
$\frac{2}{3}$
20
$\frac{2}{3}$
$\frac{12}{5}$

二、想一想，填一填。
1. $5068 = (\ \ ) × 5 + (\ \ ) × 6 + (\ \ ) × 8$
2. $404.04 = (\ \ ) × 4 + (\ \ ) × 4 + (\ \ ) × 4$
3. $62.097 = (\ \ ) × 6 + (\ \ ) × 2 + (\ \ ) × 9 + (\ \ ) × 7$
4. $2.6 = 0.1 × (\ \ ) = 0.01 × (\ \ ) = 0.001 × (\ \ )$
5. $\frac{5}{8} = (\ \ ) × 5 = (\ \ ) × 10 = (\ \ ) × 20$
6. $\frac{7}{12} = (\ \ ) × 7 = (\ \ ) × 21 = (\ \ ) × 70$

1. 1000 10 1
2. 100 1 0.01
3. 10 1 0.01 0.001
4. 26 260 2600
5. $\frac{1}{8}$ $\frac{1}{16}$ $\frac{1}{32}$
6. $\frac{1}{12}$ $\frac{1}{36}$ $\frac{1}{120}$