一、口算。
1. $68 + 4.52 =$
7. $63 - 2.23 =$
$35×70 =$
$100×5.08 =$
$\frac{4}{5}÷8 =$
$\frac{5}{3}÷\frac{25}{9} =$
$\frac{1}{4}×\frac{2}{3} =$
$\frac{6}{7}÷\frac{4}{9} =$
$7.5×0.4 =$
$2.2÷0.11 =$
$252÷3 =$
$6.5 + 3.45 =$
$\frac{3}{5}×\frac{10}{9} =$
$\frac{6}{7} - \frac{1}{6} =$
$\frac{3}{4}÷\frac{3}{16} =$
$\frac{13}{15} - \frac{2}{5} =$
$4.5 - 3×0.3 =$
$0.6×1.2÷0.04 =$
$2.4 - 1.15 + 1.6 =$
$4.5×2÷4.5×2 =$
$83×\frac{1}{83} - \frac{4}{5} =$
$25 - 36×\frac{2}{9} =$
$\frac{3}{4}÷\frac{9}{10}×\frac{3}{5} =$
$\frac{1}{5}×\frac{1}{8}÷\frac{1}{10} =$

1. 6.2
2. 3
3. 3.6
4. 5.4
5. 20
6. 18
7. 2450
8. 84
9. 2.85
10. 508
11. 9.95
12. 4
13. $\frac{1}{10}$
14. $\frac{2}{3}$
15. $\frac{1}{5}$
16. $\frac{3}{5}$
17. $\frac{29}{42}$
18. 17
19. $\frac{1}{6}$
20. 4
21. $\frac{1}{2}$
22. $\frac{27}{14}$
23. $\frac{7}{15}$
24. $\frac{1}{4}$

二、计算下面各图形中涂色部分的面积。
1.
2.

1. $8×6÷2+6×6-3.14×6^2÷4=31.74(\mathrm{cm}^2)$
2. $12×6=72(\mathrm{cm}^2)$