一、口算。
$2^2 - 1^2 =$
$3^2 - 2^2 =$
$5^2 - 4^2 =$
$6^2 - 5^2 =$
$7^2 - 6^2 =$
$8^2 - 5^2 =$
$9^2 - 4^2 =$
$12^2 - 10^2 =$
$488 ÷ 8 =$
$7.2 ÷ 0.08 =$
$0.87 + 0.3 =$
$8 × 1.25 =$
$5.5 - 0.9 =$
$705 × 2 =$
$2.4 × 0.5 =$
$0.65 ÷ 1.3 =$
$3.14 × (4^2 - 3^2) =$
$3.14 × (6^2 - 4^2) =$
$3.14 × (7^2 - 3^2) =$
$3.14 × (11^2 - 9^2) =$
$3.14 × (0.6 ÷ 2)^2 =$
$3.14 × (20 ÷ 2)^2 =$
$3.14 × (60 ÷ 3)^2 =$
$3.14 × (14 ÷ 7)^2 =$

1. 3
2. 5
3. 9
4. 11
5. 13
6. 39
7. 65
8. 44
9. 61
10. 90
11. 1.17
12. 10
13. 4.6
14. 1410
15. 1.2
16. 0.5
17. 21.98
18. 62.8
19. 125.6
20. 125.6
21. 0.2826
22. 314
23. 1256
24. 12.56

二、计算下面各图形中涂色部分的面积。
1.
2.

1. $3.14 × (8^2 - 4^2) = 150.72(\mathrm{dm}^2)$
2. $10 × 8 - 3.14 × (8 ÷ 2)^2 = 29.76(\mathrm{cm}^2)$