一、口算。
84 - 42 =
13 × 6 =
99 ÷ 3 =
6.4 + 6 =
72 ÷ 24 =
13.9 - 3.9 =
7 × 110 =
5.5 + 0.9 =
70 × 70 =
6.68 - 1.5 =
680 ÷ 2 =
12.6 - 0.8 =
639 ÷ 9 =
3.52 + 2.4 =
1900 × 5 =
0.72 + 0.24 =
17 × 30 =
650 ÷ 5 =
11 × 300 =
17 + 930 =
0.67 + 1.24 =
3.9 + 0.39 =
804 ÷ 6 =
120 × 40 =
20.5 + 2.05 =
260 ÷ 20 =
0.8 - 0.35 =
103 × 50 =
10 - 0.01 =
560 ÷ 14 =

84 - 42 = 42
13 × 6 = 78
99 ÷ 3 = 33
6.4 + 6 = 12.4
72 ÷ 24 = 3
13.9 - 3.9 = 10
7 × 110 = 770
5.5 + 0.9 = 6.4
70 × 70 = 4900
6.68 - 1.5 = 5.18
680 ÷ 2 = 340
12.6 - 0.8 = 11.8
639 ÷ 9 = 71
3.52 + 2.4 = 5.92
1900 × 5 = 9500
0.72 + 0.24 = 0.96
17 × 30 = 510
650 ÷ 5 = 130
11 × 300 = 3300
17 + 930 = 947
0.67 + 1.24 = 1.91
3.9 + 0.39 = 4.29
804 ÷ 6 = 134
120 × 40 = 4800
20.5 + 2.05 = 22.55
260 ÷ 20 = 13
0.8 - 0.35 = 0.45
103 × 50 = 5150
10 - 0.01 = 9.99
560 ÷ 14 = 40

二、计算下面各平行四边形的面积。
1.
2.

1. $63×25=1575(\mathrm{m}^2)$
2. $26×12=312(\mathrm{dm}^2)$