一、口算。
$3.7 - 1.2 =$
$55 + 37 =$
$2.8 ÷ 2 =$
$0.32 ÷ 10 =$
$2.3y - y =$
$5.5 × 2 =$
$0.32 × 2 =$
$624 ÷ 8 =$
$2.336 × 10 =$
$9.81 + 4.2 =$
$68 × c ÷ 4 =$
$19.2 ÷ 16 =$
$121 × 30 =$
$8.01 + 0.17 =$
$45 × 80 =$
$5.35 - 4.35 =$
$10.4 × 2 =$
$237 - 34 =$
$1.19 ÷ 7 =$
$1.08 - 0.89 =$
$0.05 × 800 =$
$4 ÷ 50 =$
$0.6m × 8m =$
$336 ÷ 14 =$

1. 2.5
2. 92
3. 1.4
4. 0.032
5. 1.3y
6. 11
7. 0.64
8. 78
9. 23.36
10. 14.01
11. 17c
12. 1.2
13. 3630
14. 8.18
15. 3600
16. 1
17. 20.8
18. 203
19. 0.17
20. 0.19
21. 40
22. 0.08
23. 4.8m²
24. 24

二、计算下面各题。
$4.35 + 7.5 ÷ 25$
$20 - 1.84 ÷ 2$
$(16.8 + 1.47) ÷ 7$
$63 ÷ 14 - 0.236$
$6.89 ÷ 5 + 8.622$
$12.4 ÷ (46 - 38)$

1. 4.65
2. 19.08
3. 2.61
4. 4.264
5. 10
6. 1.55