一、算一算。
1.直接写得数。
0.3+0.8=
3.6-2.6=
3.1-2.7=
1.6+3.8=
8.6-2.5=
0.12+0.28=
12.9+3.6=
2.7-0.9=
3.47+0.53=
8-0.8=
1.5-0.9=
4.1-3.6=

0.3+0.8=1.1
3.6-2.6=1
3.1-2.7=0.4
1.6+3.8=5.4
8.6-2.5=6.1
0.12+0.28=0.4
12.9+3.6=16.5
2.7-0.9=1.8
3.47+0.53=4
8-0.8=7.2
1.5-0.9=0.6
4.1-3.6=0.5

2. 用竖式计算。
16.38+25.8=
20-10.76=
20.08+1.07=
9.3-2.85=
3.67+8.56=
30-12.57=

1. $16.38+25.8=42.18$
```
16.38
+ 25.80
--------
42.18
```
2. $20-10.76=9.24$
```
20.00
10.76
--------
9.24
```
3. $20.08+1.07=21.15$
```
20.08
+ 1.07
--------
21.15
```
4. $9.3-2.85=6.45$
```
9.30
2.85
--------
6.45
```
5. $3.67+8.56=12.23$
```
3.67
+ 8.56
--------
12.23
```
6. $30-12.57=17.43$
```
30.00
12.57
--------
17.43
```

3. 脱式计算，能简算的要简算。
8.89-(5.3+2.89)
19.57-2.36-1.64
70.9-1.25-0.75
3.73+5.2+4.8+1.27

$8.89-(5.3+2.89)$
$=8.89-2.89-5.3$
$=6-5.3$
$=0.7$
$19.57-2.36-1.64$
$=19.57-(2.36+1.64)$
$=19.57-4$
$=15.57$
$70.9-1.25-0.75$
$=70.9-(1.25+0.75)$
$=70.9-2$
$=68.9$
$3.73+5.2+4.8+1.27$
$=(3.73+1.27)+(5.2+4.8)$
$=5+10$
$=15$