一、口算。
1.25×2 =
6.4÷0.4 =
1.28 + 0.82 =
2.7 + 0.3 =
0.21×0.5 =
21.5 - 9.5 =
16÷80 =
0.5 - 0.25 =
680÷17 =
42 + 338 =
0.6÷0.2 =
8×0.375 =
0.36÷0.3 =
15×600 =
0.87 - 0.7 =
100 - 35 =
2.6 + 1.7 =
8.4÷7 =
11÷2.2 =
7.2×0.4 =
3.2 + 14 =
0.8 + 1.02 =
540 - 34 =
1.5×0.5 =
100÷0.5 =
4.8×5 =
0.8 - 0.79 =
6.5 - 5.4 =
0.5 + 1.3 =
0.42÷0.7 =

2.5 16 2.1
3 0.105 12
0.2 0.25 40
380 3 3
1.2 9000 0.17
65 4.3 1.2
5 2.88 17.2
1.82 506 0.75
200 24 0.01
1.1 1.8 0.6

二、解方程。
3.6x - x = 3.12
0.6x - 3×5 = 24
7×2.1 + 1.2x = 18.3

$x = 1.2$ $x = 65$
$x = 3$