$\frac{5}{12} × 5 =$
$\frac{12}{25} × 4 =$
$35 × \frac{5}{7} =$
$\frac{3}{5} × \frac{6}{7} =$
$\frac{4}{13} × \frac{2}{3} =$
$\frac{5}{26} × \frac{26}{9} =$
$\frac{3}{4} × 4.8 =$
$\frac{9}{16} × 9.6 =$
$2.4 × \frac{5}{6} =$
$6.3 × \frac{5}{9} =$
$7.5 × \frac{4}{15} =$
$5.4 × \frac{5}{18} =$
$36 × \frac{4}{9} =$
$\frac{3}{7} × \frac{7}{9} =$
$\frac{5}{12} × 3.6 =$
$\frac{2}{27} × 9 =$

1. $\frac{25}{12}$
2. $\frac{48}{25}$
3. 25
4. $\frac{18}{35}$
5. $\frac{8}{39}$
6. $\frac{5}{9}$
7. 3.6
8. 5.4
9. 2
10. 3.5
11. 2
12. 1.5
13. 16
14. $\frac{1}{3}$
15. 1.5
16. $\frac{2}{3}$

2 脱式计算（能简算的要简算）
建议用时4分钟 评价：☆☆☆
$\frac{5}{9} + \frac{28}{3} × \frac{4}{15}$
$\frac{11}{27} × \frac{53}{42} × \frac{54}{11}$
$\frac{3}{5} × (1 - \frac{1}{4}) × \frac{4}{9}$
$16 × (\frac{15}{16} - \frac{3}{4})$
$\frac{5}{8} × \frac{15}{17} + \frac{15}{17} × \frac{3}{8}$
$99 × \frac{5}{98}$

1. $\frac{137}{45}$
2. $\frac{53}{21}$
3. $\frac{1}{5}$
4. 3
5. $\frac{15}{17}$
6. $5\frac{5}{98}$

交换分子法 根据$\frac{a}{b}×\frac{c}{d}=\frac{c}{b}×\frac{a}{d}$（a，b，c，d均不为0）简便计算。
$\frac{13}{49}×21 + 13×\frac{28}{49}$
$\frac{7}{17}×\frac{16}{25} + \frac{9}{17}×\frac{7}{25}$

1. 13
2. $\frac{7}{17}$