一、填空题
1. $5×(-9)=$
2. $(-4)×(-0.25)=$
3. $(-\dfrac{5}{2})×(-\dfrac{10}{3})=$
4. $(-6)×(-\dfrac{1}{2})=$
5. $(-7.6)×0.5=$
6. $(+4.5)×(-1\dfrac{1}{2})=$
7. $-\dfrac{2}{3}$的倒数是 .
8. $-4.25$的倒数是 .

1. -45
2. 1
3. $\dfrac{25}{3}$
4. 3
5. -3.8
6. $-\dfrac{27}{4}$
7. $-\dfrac{3}{2}$
8. $-\dfrac{4}{17}$

二、计算题
9. $-\dfrac{5}{24} × (-1\dfrac{3}{5})$
10. $(-2.25) × (+80)$
11. $(-15) × (-1\dfrac{2}{3})$
12. $-2\dfrac{4}{15} × 25$
13. $(-3\dfrac{1}{2}) × (-2\dfrac{1}{3})$
14. $(-0.25) × (+1\dfrac{1}{15})$
15. $(-2\dfrac{6}{7}) × (-2.1)$
16. $\left| -\dfrac{7}{9} \right| × (-2\dfrac{1}{4})$

9. $\dfrac{1}{3}$
10. -180
11. 25
12. $-\dfrac{170}{3}$
13. $\dfrac{49}{6}$
14. $-\dfrac{4}{15}$
15. 6
16. $-\dfrac{7}{4}$