一、口算。
$2.6 - 1.55 =$
$0.39 × 50 =$
$12 - 6.2 - 3.8 =$
$3.4 + 4.3 =$
$0.06 × 90 =$
$30 - 4.4 × 5 =$
$228 ÷ 4 =$
$7.5 - 5.65 =$
$0.07 × 0.8 × 100 =$
$0.9 + 2.01 =$
$1.25 × 0.8 =$
$2.8 ÷ (0.14 + 0.26) =$
$2.7 ÷ 10 =$
$64 ÷ 0.4 =$
$2.8 × 1.2 ÷ 7 =$
$\frac{5}{9} × \frac{3}{5} =$
$\frac{1}{5} + \frac{7}{40} =$
$\frac{1}{2} × \frac{4}{5} × \frac{1}{2} =$
$10 ÷ \frac{5}{24} =$
$\frac{7}{16} ÷ \frac{1}{4} =$
$\frac{1}{4} × 8.5 × 4 =$
$\frac{3}{5} - \frac{3}{7} =$
$\frac{2}{3} × \frac{3}{7} =$
$48 × (\frac{3}{4} - \frac{1}{2}) =$

1. 1.05
2. 19.5
3. 2
4. 7.7
5. 5.4
6. 8
7. 57
8. 1.85
9. 5.6
10. 2.91
11. 1
12. 7
13. 0.27
14. 160
15. 0.48
16. $\frac{1}{3}$
17. $\frac{3}{8}$
18. $\frac{1}{5}$
19. 48
20. $\frac{7}{4}$
21. 8.5
22. $\frac{6}{35}$
23. $\frac{2}{7}$
24. 12

二、计算下面各图形中涂色部分的面积。
1.
2.

1. $3.14×(4÷2)^2×2=25.12(\mathrm{dm}^2)$
2. $(3+3)×(3+3)-3.14×3^2=7.74(\mathrm{cm}^2)$