一、口算。
$0.5 - 0.15 =$
$4.8 + 8.4 =$
$1.4 × 30 =$
$780 ÷ 20 =$
$4.5 + 0.36 =$
$54 × 0.01 =$
$0.54 ÷ 9 =$
$388 + 298 =$
$2 - 1.6 =$
$9.25 + 9.25 =$
$4.08 × 5 =$
$7.3 - 5.25 =$
$2.6 ÷ 5 =$
$11 × 0.05 =$
$2.4 × 0.4 =$
$\frac{8}{15} - \frac{2}{5} =$
$\frac{29}{30} - \frac{3}{10} =$
$\frac{1}{4} + \frac{5}{6} =$
$\frac{3}{4} - \frac{2}{5} =$
$\frac{6}{7} + \frac{5}{6} =$
$\frac{17}{18} - \frac{8}{9} =$
$\frac{9}{10} + \frac{4}{5} =$
$\frac{7}{16} + \frac{5}{8} =$
$\frac{3}{5} - \frac{1}{4} =$

1. 0.35
2. 13.2
3. 42
4. 39
5. 4.86
6. 0.54
7. 0.06
8. 686
9. 0.4
10. 18.5
11. 20.4
12. 2.05
13. 0.52
14. 0.55
15. 0.96
16. $\frac{2}{15}$
17. $\frac{2}{3}$
18. $\frac{13}{12}$
19. $\frac{7}{20}$
20. $\frac{71}{42}$
21. $\frac{1}{18}$
22. $\frac{17}{10}$
23. $\frac{17}{16}$
24. $\frac{7}{20}$

二、计算下面各题，能用简便算法的就用简便算法。
2.8×3.1−17.6÷8
0.8×9.9×1.25
6.87×[40÷(3.8−3.4)]
8.59×101
99×6.5+6.5
1.56×1.7+4.4×0.17

1. 6.48
2. 9.9
3. 687
4. 867.59
5. 650
6. 3.4