一、口算。
$4 - 1.99 =$
$0.38 × 200 =$
$720 ÷ 40 =$
$7.34 × 5 =$
$7.5 × 20 =$
$77.2 - 32.1 =$
$9.06 ÷ 0.3 =$
$2.7 ÷ 0.27 =$
$6.66 ÷ 20 =$
$901 - 377 =$
$710 + 595 =$
$600 × 0.09 =$
$\frac{3}{4} + \frac{1}{5} =$
$\frac{11}{4} × \frac{2}{11} =$
$\frac{2}{3} ÷ \frac{3}{20} =$
$\frac{5}{2} ÷ \frac{1}{4} =$
$12 × \frac{5}{6} =$
$\frac{2}{15} + 0.15 =$
$12 ÷ \frac{3}{4} =$
$\frac{3}{4} + \frac{3}{20} =$
$\frac{1}{2} × \frac{1}{10} =$
$0.75 ÷ \frac{2}{5} =$
$\frac{5}{8} ÷ \frac{5}{12} =$
$\frac{5}{8} - \frac{3}{5} =$

1. 2.01
2. 76
3. 18
4. 36.7
5. 150
6. 45.1
7. 30.2
8. 10
9. 0.333
10. 524
11. 1305
12. 54
13. $\frac{19}{20}$
14. $\frac{1}{2}$
15. $\frac{40}{9}$
16. 10
17. 10
18. $\frac{17}{60}$
19. 16
20. $\frac{9}{10}$
21. $\frac{1}{20}$
22. $\frac{15}{8}$
23. $\frac{3}{2}$
24. $\frac{1}{40}$

二、根据比例的基本性质，在括号里填合适的数。
$\frac{5}{7}:( )=\frac{5}{8}:\frac{7}{9}$
$\frac{1}{15}:\frac{1}{3}=\frac{4}{5}:( )$
$\frac{8}{9}:( )=\frac{1}{2}:\frac{3}{4}$
$0.85:( )=\frac{1}{2}:2$
$35:( )=\frac{7}{8}:6$
$\frac{8}{21}:16=\frac{2}{7}:( )$
$\frac{1}{6}:\frac{5}{9}=( ):\frac{2}{3}$
$\frac{5}{9}:( )=\frac{1}{3}:\frac{6}{5}$
$\frac{3}{4}:( )=\frac{6}{5}:\frac{9}{4}$
$( ):4=\frac{1}{6}:7$
$0.6:( )=0.2:7.5$
$2.8:\frac{7}{8}=56:( )$
$( ):6=22.5:9$
$6:15=( ):\frac{2}{3}$
$\frac{5}{8}:\frac{3}{4}=( ):\frac{6}{7}$

1. $\frac{8}{9}$
2. $4$
3. $\frac{4}{3}$
4. $3.4$
5. $240$
6. $12$
7. $\frac{1}{5}$
8. $2$
9. $\frac{45}{32}$
10. $\frac{2}{21}$
11. $22.5$
12. $17.5$
13. $15$
14. $\frac{4}{15}$
15. $\frac{5}{7}$