一、口算。
$205×6 =$
$16 - 0.16 =$
$48 ÷ 0.06 =$
$2×0.58 =$
$0.6×12 =$
$15.7 + 13.8 =$
$254 - 45 =$
$77 + 7 =$
$0.04×70 =$
$405 ÷ 9 =$
$10.5 ÷ 100 =$
$7.61 + 2.39 =$
$7 ÷ \frac{7}{15} =$
$\frac{7}{5} ÷ \frac{21}{10} =$
$\frac{3}{20} + \frac{1}{4} =$
$\frac{9}{10} ÷ \frac{1}{5} =$
$\frac{4}{9} × \frac{3}{4} =$
$\frac{1}{24} ÷ \frac{1}{12} =$
$30 × \frac{2}{5} =$
$0.5 - \frac{3}{14} =$
$\frac{9}{5} × \frac{5}{6} =$
$\frac{3}{4} ÷ \frac{3}{2} =$
$\frac{1}{5} - \frac{1}{6} =$
$\frac{7}{24} × 0.75 =$

1. 1230
2. 15.84
3. 800
4. 1.16
5. 7.2
6. 29.5
7. 209
8. 84
9. 2.8
10. 45
11. 0.105
12. 10
13. 15
14. $\frac{2}{3}$
15. $\frac{2}{5}$
16. $\frac{9}{2}$
17. $\frac{1}{3}$
18. $\frac{1}{2}$
19. 12
20. $\frac{2}{7}$
21. $\frac{3}{2}$
22. $\frac{1}{2}$
23. $\frac{1}{30}$
24. $\frac{7}{32}$

二、把下面的二进制数改写成十进制数。
$(1101)_2$
$(10100)_2$
$(11011)_2$
$(101101)_2$
$(10010111)_2$
$(11000101)_2$

1. 13
2. 20
3. 27
4. 45
5. 151
6. 197