一、口算。
$30.45 - 20.55 =$
$125 ÷ 1000 =$
$4.5 × 0.8 =$
$6.93 - 5.13 =$
$936 + 764 =$
$1338 - 926 =$
$4.08 × 0.4 =$
$0.88 ÷ 0.8 =$
$16.2 × 5 =$
$8.5 ÷ 17 =$
$7.32 + 5.28 =$
$12.05 ÷ 5 =$
$\frac{5}{6} + \frac{4}{9} =$
$\frac{5}{6} × \frac{7}{8} =$
$20 ÷ \frac{5}{6} =$
$\frac{5}{13} × \frac{13}{15} =$
$\frac{8}{9} × \frac{3}{4} =$
$\frac{9}{4} ÷ \frac{3}{4} =$
$\frac{7}{8} ÷ \frac{1}{16} =$
$\frac{4}{9} ÷ \frac{2}{3} =$
$\frac{4}{9} × 18 =$
$1.25 × \frac{8}{5} =$
$\frac{10}{21} × \frac{7}{15} =$
$\frac{2}{7} + \frac{5}{8} =$

1. 9.9
2. 0.125
3. 3.6
4. 1.8
5. 1700
6. 412
7. 1.632
8. 1.1
9. 81
10. 0.5
11. 12.6
12. 2.41
13. $\frac{23}{18}$
14. $\frac{35}{48}$
15. 24
16. $\frac{1}{3}$
17. $\frac{2}{3}$
18. 3
19. 14
20. $\frac{2}{3}$
21. 8
22. 2
23. $\frac{2}{9}$
24. $\frac{51}{56}$

二、计算下面各题，能简算的要简算。
$\frac{3}{4} - \frac{3}{4} ÷ 3 + \frac{9}{25}$
$\frac{5}{6} - 0.82 - 0.18 + \frac{1}{6}$
$24 × \frac{51}{43} + 51 × \frac{19}{43}$
$0.567 × 101 - 0.567$
$12.5 × 2.5 × 40 × 0.8$
$41.6 ÷ (13.94 + 34.3 × 0.2)$

1. $\frac{43}{50}$
2. 0
3. 51
4. 56.7
5. 1000
6. 2