一、口算。
6.6 - 4.4 =
71 + 39 =
18 × 2 =
57 ÷ 19 =
7.2 - 2.7 =
3.6 + 5 =
9.6 - 1.6 =
24 × 7 =
74 - 47 =
13 × 30 =
170 ÷ 5 =
3.4 + 4.6 =
436 ÷ 4 =
0.78 + 2.2 =
440 × 3 =
340 - 180 =
409 × 2 =
560 + 60 =
560 ÷ 80 =
1.87 - 0.97 =
335 ÷ 5 =
4.15 - 0.05 =
29 × 200 =
5.8 + 0.84 =
125 × 6 =
2.08 - 1.8 =
450 × 40 =
5 - 0.28 =
300 ÷ 20 =
112 ÷ 16 =

6.6 - 4.4 = 2.2
71 + 39 = 110
18 × 2 = 36
57 ÷ 19 = 3
7.2 - 2.7 = 4.5
3.6 + 5 = 8.6
9.6 - 1.6 = 8
24 × 7 = 168
74 - 47 = 27
13 × 30 = 390
170 ÷ 5 = 34
3.4 + 4.6 = 8
436 ÷ 4 = 109
0.78 + 2.2 = 2.98
440 × 3 = 1320
340 - 180 = 160
409 × 2 = 818
560 + 60 = 620
560 ÷ 80 = 7
1.87 - 0.97 = 0.9
335 ÷ 5 = 67
4.15 - 0.05 = 4.1
29 × 200 = 5800
5.8 + 0.84 = 6.64
125 × 6 = 750
2.08 - 1.8 = 0.28
450 × 40 = 18000
5 - 0.28 = 4.72
300 ÷ 20 = 15
112 ÷ 16 = 7

二、计算下面各三角形的面积。
1.
2.

1. 13×4÷2=26(cm²)
2. 30×21÷2=315(m²)