一、口算。
$18.9 + 0.21 =$
$7.56 - 3.12 =$
$9.5 ÷ 0.5 ÷ 2 =$
$0.68 ÷ 4 =$
$714 ÷ 7 =$
$8 × 21 × 1.25 =$
$7.7 ÷ 77 =$
$14 ÷ 20 =$
$6.66 + 2 × 0.8 =$
$3.64 × 20 =$
$0.9 - 0.09 =$
$3.95 + 2.4 × 0.5 =$
$0.46 × 0.2 =$
$2.75 + 32.5 =$
$(13.5 - 12.5) ÷ 2 =$
$\frac{2}{9} ÷ \frac{1}{2} =$
$\frac{3}{4} × \frac{16}{15} =$
$( \frac{9}{10} - \frac{2}{5} ) ÷ 4 =$
$\frac{7}{8} × \frac{12}{13} =$
$\frac{9}{32} ÷ \frac{3}{4} =$
$24 × ( \frac{3}{5} ÷ \frac{1}{5} ) =$
$0.6 × \frac{10}{11} =$
$\frac{1}{2} + \frac{1}{5} =$
$\frac{2}{3} × 0.25 ÷ \frac{3}{50} =$

1. 19.11
2. 4.44
3. 9.5
4. 0.17
5. 102
6. 210
7. 0.1
8. 0.7
9. 8.26
10. 72.8
11. 0.81
12. 5.15
13. 0.092
14. 35.25
15. 0.5
16. $\frac{4}{9}$
17. $\frac{4}{5}$
18. $\frac{1}{8}$
19. $\frac{21}{26}$
20. $\frac{3}{8}$
21. 72
22. $\frac{6}{11}$
23. $\frac{7}{10}$
24. $\frac{25}{9}$

二、计算下面各题，能简算的要简算。
$2025\frac{2025}{2026} ÷ 2025$
$\frac{9}{10} ÷ \frac{3}{4} × \frac{5}{4} ÷ \frac{5}{6}$
$( \frac{1}{6} + \frac{2}{15} ) ÷ \frac{2}{5} - \frac{5}{12}$
$8.6 × 10.1$
$71.4 ÷ (100 × 0.42) + 20.5$
$4.08 ÷ (18.9 ÷ 18 - 0.75)$

1. $1\frac{1}{2026}$
2. $\frac{9}{5}$
3. $\frac{1}{3}$
4. 86.86
5. 22.2
6. 13.6