一、口算。
$720×3=$
$2.25+6.25=$
$2.2×0.3=$
$8.8×0.1=$
$2.8÷0.04=$
$1.96÷0.2=$
$7.93-3.43=$
$5.4+5.04=$
$1.54+4.56=$
$350-289=$
$31.4÷3.14=$
$2.64÷1.1=$
$\frac{5}{8} - \frac{1}{2} =$
$\frac{2}{5} ÷ \frac{4}{11} =$
$\frac{17}{18} × \frac{9}{11} =$
$25 ÷ \frac{5}{6} =$
$\frac{3}{4} × \frac{4}{5} =$
$\frac{3}{4} ÷ 0.4 =$
$\frac{15}{16} × \frac{8}{9} =$
$\frac{15}{4} ÷ \frac{3}{2} =$
$0.8 × \frac{5}{8} =$
$\frac{4}{5} × \frac{1}{3} =$
$\frac{1}{12} + \frac{4}{15} =$
$0.625 - \frac{1}{3} =$

1. $720×3=2160$
2. $2.25+6.25=8.5$
3. $2.2×0.3=0.66$
4. $8.8×0.1=0.88$
5. $2.8÷0.04=70$
6. $1.96÷0.2=9.8$
7. $7.93-3.43=4.5$
8. $5.4+5.04=10.44$
9. $1.54+4.56=6.1$
10. $350-289=61$
11. $31.4÷3.14=10$
12. $2.64÷1.1=2.4$
13. $\frac{5}{8} - \frac{1}{2} =\frac{1}{8}$
14. $\frac{2}{5} ÷ \frac{4}{11} =\frac{11}{10}$
15. $\frac{17}{18} × \frac{9}{11} =\frac{17}{22}$
16. $25 ÷ \frac{5}{6} =30$
17. $\frac{3}{4} × \frac{4}{5} =\frac{3}{5}$
18. $\frac{3}{4} ÷ 0.4 =\frac{15}{8}$
19. $\frac{15}{16} × \frac{8}{9} =\frac{5}{6}$
20. $\frac{15}{4} ÷ \frac{3}{2} =\frac{5}{2}$
21. $0.8 × \frac{5}{8} =\frac{1}{2}$
22. $\frac{4}{5} × \frac{1}{3} =\frac{4}{15}$
23. $\frac{1}{12} + \frac{4}{15} =\frac{7}{20}$
24. $0.625 - \frac{1}{3} =\frac{7}{24}$

二、把下面各比化成最简整数比，并求出比值。
$0.75:5$
$\frac{3}{4}:\frac{7}{8}$
$\frac{2}{3}$时：45分
$1.26:0.04$
$\frac{16}{5}:\frac{8}{15}$
320米：0.4千米

1. $0.75:5$ 最简整数比为$3:20$，比值为$\frac{3}{20}$
2. $\frac{3}{4}:\frac{7}{8}$ 最简整数比为$6:7$，比值为$\frac{6}{7}$
3. $\frac{2}{3}$时：45分 最简整数比为$8:9$，比值为$\frac{8}{9}$
4. $1.26:0.04$ 最简整数比为$63:2$，比值为$\frac{63}{2}$
5. $\frac{16}{5}:\frac{8}{15}$ 最简整数比为$6:1$，比值为$6$
6. 320米：0.4千米 最简整数比为$4:5$，比值为$\frac{4}{5}$