一、口算。
2.35 + 76.5 =
4.8 ÷ 0.8 =
3.14 × 0.8 =
0.34 × 0.5 =
5.7 + 3.3 =
0.628 ÷ 3.14 =
2.4 ÷ 12 =
7.2 ÷ 0.4 =
$3.14 × 4^2 =$
0.97 - 0.45 =
0.67 + 0.33 =
3.768 ÷ 3.14 =
7.25 + 2.75 =
3 × 1.06 =
3.14 × 40 =
0.125 × 16 =
8 ÷ 0.01 =
188.4 ÷ 3.14 =
0.39 + 0.64 =
2.25 ÷ 0.5 =
2.198 ÷ 3.14 =
4.4 × 0.4 =
4.57 - 3.5 =
56.52 ÷ 3.14 =

78.85
6
2.512
0.17
9
0.2
0.2
18
50.24
0.52
1
1.2
10
3.18
125.6
2
800
60
1.03
4.5
0.7
1.76
1.07
18

二、计算下面各图形的周长和面积。
1.
2.

1. 周长: $3.14 × 2 = 6.28(\mathrm{dm})$
面积: $3.14 × (2 ÷ 2)^2 = 3.14(\mathrm{dm}^2)$
2. 周长: $2 × 3.14 × 0.5 = 3.14(\mathrm{cm})$
面积: $3.14 × 0.5^2 = 0.785(\mathrm{cm}^2)$