一、口算。
$4 - 1.09 =$
$3.8 + 6.2 =$
$1.03 × 6 =$
$35 × 200 =$
$4.1 × 200 =$
$525 - 199 =$
$35 ÷ 0.01 =$
$8.8 ÷ 0.11 =$
$3.42 - 1.88 =$
$66 - 6.6 =$
$0.72 + 0.8 =$
$2.5 × 0.7 =$
$0.25 × 80 =$
$3.6 ÷ 30 =$
$10.2 ÷ 3 =$
$\frac{7}{8} - \frac{7}{11} =$
$\frac{1}{7} + \frac{7}{5} =$
$\frac{4}{15} + \frac{1}{5} =$
$\frac{2}{3} + \frac{1}{4} =$
$\frac{5}{6} - \frac{1}{2} =$
$\frac{4}{7} + \frac{1}{3} =$
$\frac{4}{5} + \frac{2}{3} =$
$\frac{9}{16} + \frac{3}{4} =$
$\frac{4}{5} - \frac{1}{6} =$

1. 2.91
2. 10
3. 6.18
4. 7000
5. 820
6. 326
7. 3500
8. 80
9. 1.54
10. 59.4
11. 1.52
12. 1.75
13. 20
14. 0.12
15. 3.4
16. $\frac{21}{88}$
17. $\frac{54}{35}$
18. $\frac{7}{15}$
19. $\frac{11}{12}$
20. $\frac{1}{3}$
21. $\frac{19}{21}$
22. $\frac{22}{15}$
23. $\frac{21}{16}$
24. $\frac{19}{30}$

二、计算下面各题，能用简便算法的就用简便算法。
$\frac{5}{6} + \frac{3}{4} - \frac{1}{2}$
$1\frac{3}{7} - \frac{5}{17} - \frac{12}{17}$
$\frac{5}{6} + \frac{5}{7} - \frac{5}{6} + \frac{5}{7}$
$\frac{15}{16} - (\frac{5}{12} + \frac{1}{6})$
$\frac{13}{49} + (\frac{36}{49} - \frac{17}{35})$
$\frac{15}{16} - \frac{1}{3} + \frac{1}{16} - \frac{2}{9}$

1. $\frac{13}{12}$
2. $\frac{3}{7}$
3. $\frac{10}{7}$
4. $\frac{17}{48}$
5. $\frac{18}{35}$
6. $\frac{4}{9}$