一、口算。
$2^2 - 1^2 =$
$3^2 - 2^2 =$
$5^2 - 4^2 =$
$6^2 - 5^2 =$
$7^2 - 6^2 =$
$8^2 - 5^2 =$
$9^2 - 4^2 =$
$12^2 - 10^2 =$
$5.5 - 0.9 =$
$8 × 1.25 =$
$7.2 ÷ 0.08 =$
$0.87 + 0.3 =$
$4.8 ÷ 0.06 =$
$2.4 × 0.5 =$
$0.65 ÷ 1.3 =$
$0.75 × 0.2 =$
$3.14 × (7^2 - 3^2) =$
$3.14 × (4^2 - 3^2) =$
$3.14 × (6^2 - 4^2) =$
$3.14 × (0.6 ÷ 2)^2 =$
$3.14 × (60 ÷ 3)^2 =$
$3.14 × (11^2 - 9^2) =$
$3.14 × (20 ÷ 2)^2 =$
$3.14 × (14 ÷ 7)^2 =$

3
4.6
125.6
5
10
21.98
9
90
62.8
11
1.17
0.2826
13
80
1256
39
1.2
125.6
65
0.5
314
44
0.15
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. $3.14×2^2÷4=3.14(\mathrm{cm}^2)$