一、口算。
$7.2 ÷ 20 =$
$2 - 1.25 =$
$7.7 + 3.3 =$
$3.68 + 0.27 =$
$4.4 × 5 =$
$5.4 ÷ 0.9 =$
$1.4 ÷ 0.07 =$
$5.5 ÷ 55 =$
$11 - 3.7 =$
$\frac{3}{8} + \frac{1}{5} =$
$\frac{9}{10} - \frac{3}{4} =$
$\frac{5}{4} - \frac{1}{2} =$
$\frac{1}{3} - \frac{2}{9} =$
$\frac{2}{3} - \frac{1}{4} =$
$\frac{2}{5} + \frac{4}{7} =$
$36 × \frac{7}{24} =$
$14 × \frac{8}{7} =$
$\frac{5}{7} × 21 =$
$10 × \frac{3}{5} =$
$2 × \frac{7}{8} =$
$\frac{3}{7} × 49 =$
$\frac{5}{22} × 11 =$
$\frac{3}{5} × 2 =$
$50 × \frac{2}{25} =$

1. 0.36
2. 0.75
3. 11
4. 3.95
5. 22
6. 6
7. 20
8. 0.1
9. 7.3
10. $\frac{23}{40}$
11. $\frac{3}{20}$
12. $\frac{3}{4}$
13. $\frac{1}{9}$
14. $\frac{5}{12}$
15. $\frac{34}{35}$
16. $\frac{21}{2}$
17. 16
18. 15
19. 6
20. $\frac{7}{4}$
21. 21
22. $\frac{5}{2}$
23. $\frac{6}{5}$
24. 4

二、计算下面各题。
$\frac{2}{9} + \frac{17}{45} - \frac{2}{5}$
$15.4 ÷ 0.5 - 12 × 0.3$
$7.2 × (18.5 - 8.5 ÷ 0.5)$
$\frac{7}{8} - (\frac{2}{3} + \frac{1}{6})$
$9.5 ÷ 2.5 × (2.8 ÷ 0.7)$
$7.24 × [2.9 ÷ (31 - 16.5)]$

1. $\frac{1}{5}$
2. 27.2
3. 10.8
4. $\frac{1}{24}$
5. 15.2
6. 1.448