一、口算。
$5.2 - 2.72 =$
$0.13 × 40 =$
$(6.3 + 1.7) ÷ 0.4 =$
$3.29 + 2.8 =$
$880 ÷ 11 =$
$7.7 ÷ 77 × 10 =$
$0.04 × 500 =$
$29.5 - 5.9 =$
$3.42 × 0.2 - 0.2 =$
$24.8 ÷ 80 =$
$20.3 + 7.7 =$
$120 × 0.25 × 0.4 =$
$6 ÷ \frac{6}{7} =$
$\frac{1}{3} + 0.75 =$
$( \frac{7}{12} + \frac{3}{8} ) ÷ \frac{1}{48} =$
$\frac{4}{5} × \frac{3}{4} =$
$\frac{2}{3} ÷ \frac{5}{6} =$
$\frac{2}{5} ÷ \frac{6}{7} × \frac{3}{8} =$
$0.6 ÷ \frac{5}{8} =$
$\frac{6}{7} - \frac{2}{3} =$
$\frac{3}{4} × 8 × \frac{1}{2} =$
$\frac{5}{8} + \frac{3}{4} =$
$\frac{14}{19} ÷ \frac{7}{19} =$
$1 ÷ \frac{2}{5} × \frac{2}{5} =$

1. 2.48
2. 5.2
3. 20
4. 6.09
5. 80
6. 1
7. 20
8. 23.6
9. 0.484
10. 0.31
11. 28
12. 12
13. 7
14. $\frac{13}{12}$
15. 46
16. $\frac{3}{5}$
17. $\frac{4}{5}$
18. $\frac{7}{40}$
19. $\frac{24}{25}$
20. $\frac{4}{21}$
21. 3
22. $\frac{11}{8}$
23. 2
24. 1

二、计算下面各题，能简算的要简算。
$(\dfrac{5}{8} - \dfrac{1}{4}) × (\dfrac{8}{9} ÷ \dfrac{4}{15})$
$\dfrac{3}{5} × 9.8 + 0.6 × \dfrac{1}{5}$
$(\dfrac{3}{8} - \dfrac{3}{8} ÷ \dfrac{8}{3}) × \dfrac{16}{9}$
$18.6 × 6 + 1.4 × 6$
$7.2 - 4.54 + 9.8 - 6.46$
$3.61 ÷ (7.2 - 5.3) × 30$

1. $\frac{5}{4}$
2. 6
3. $\frac{5}{12}$
4. 120
5. 6
6. 57