一、口算。
$10 - 0.1 =$
$1.5 ÷ 4 =$
$0.88 × 0.4 =$
$7.5 ÷ 0.6 =$
$65 × 60 =$
$170 ÷ 5 =$
$0.875 × 2 =$
$1.8 × 300 =$
$0.7 + 0.7 =$
$400 - 320 =$
$75 + 15 =$
$25 × 0.04 =$
$1.2 × \frac{5}{6} =$
$\frac{3}{4} ÷ \frac{6}{7} =$
$\frac{7}{24} × \frac{3}{14} =$
$\frac{5}{8} × \frac{1}{4} =$
$\frac{16}{5} ÷ \frac{8}{7} =$
$\frac{1}{8} ÷ \frac{5}{32} =$
$\frac{2}{5} + \frac{5}{12} =$
$\frac{5}{9} ÷ \frac{1}{3} =$
$\frac{7}{8} - \frac{5}{6} =$
$\frac{3}{10} × \frac{5}{12} =$
$\frac{9}{14} × \frac{7}{12} =$
$0.8 ÷ \frac{8}{15} =$

1. 9.9
2. 0.375
3. 0.352
4. 12.5
5. 3900
6. 34
7. 1.75
8. 540
9. 1.4
10. 80
11. 90
12. 1
13. 1
14. $\frac{7}{8}$
15. $\frac{1}{16}$
16. $\frac{5}{32}$
17. $\frac{14}{5}$
18. $\frac{4}{5}$
19. $\frac{49}{60}$
20. $\frac{5}{3}$
21. $\frac{1}{24}$
22. $\frac{1}{8}$
23. $\frac{3}{8}$
24. $\frac{3}{2}$

二、把下面各比化成最简整数比，并求出比值。
$\frac{42}{70}$
$80:48$
$4\mathrm{厘米}:\frac{1}{3}\mathrm{分米}$
$1.8:0.27$
$\frac{9}{25}:\frac{3}{10}$
$0.25\mathrm{时}:20\mathrm{分}$

1. 最简整数比：$3:5$，比值：$\frac{3}{5}$
2. 最简整数比：$5:3$，比值：$\frac{5}{3}$
3. 最简整数比：$6:5$，比值：$\frac{6}{5}$
4. 最简整数比：$20:3$，比值：$\frac{20}{3}$
5. 最简整数比：$6:5$，比值：$\frac{6}{5}$
6. 最简整数比：$3:4$，比值：$\frac{3}{4}$