1. 口算。
$0.8 + 6.5 =$ $0.83 + 4.6 =$ $0.98 - 0.28 =$
$7.82 + 1.1 =$ $5 - 0.3 =$ $0.45 + 0.55 =$
$9.5 - 9.45 =$ $0.48 + 0.33 =$ $10 - 3.2 =$

$0.8 + 6.5 = 7.3$
$0.83 + 4.6 = 5.43$
$0.98 - 0.28 = 0.7$
$7.82 + 1.1 = 8.92$
$5 - 0.3 = 4.7$
$0.45 + 0.55 = 1$
$9.5 - 9.45 = 0.05$
$0.48 + 0.33 = 0.81$
$10 - 3.2 = 6.8$

2. 用竖式计算。
$3.8 + 2.26 =$ $14 + 2.67 =$ $11.55 - 7.49 =$
$10 - 7.75 =$ $6.94 + 10.8 =$ $13.6 - 6 =$

3.8 + 2.26 = 6.06
```
3.80
+ 2.26
------
6.06
```
14 + 2.67 = 16.67
```
14.00
+ 2.67
------
16.67
```
11.55 - 7.49 = 4.06
```
11.55
7.49
------
4.06
```
10 - 7.75 = 2.25
```
10.00
7.75
------
2.25
```
6.94 + 10.8 = 17.74
```
6.94
+10.80
------
17.74
```
13.6 - 6 = 7.6
```
13.6
6.0
------
7.6
```

3. 先判断，再改正有错误的计算。
$\begin{array}{r}3\ 5.8\\+2.6\ 2\\\hline9.1\ 3\end{array}$ 改正： $\begin{array}{r}5\ 7\\-6.3\ 5\\\hline5\ 1.6\ 5\end{array}$ 改正：


() ()

（×）改正：$\begin{array}{r}35.80\\+2.62\\\hline38.42\end{array}$
（×）改正：$\begin{array}{r}57.00\\-6.35\\\hline50.65\end{array}$