3. 计算下面各题,能简算的要简算。
①$3.1×0.3×0.5$ ⑥$4×3.6-2.6$
②$0.4×0.7-0.15$ ⑦$9.6×1.25×80$
③$0.25×9×0.4$ ⑧$50×1.45×0.02$
④$0.6×0.4×100$ ⑨$7.5×2.4-7.5×0.4$
⑤$12×5.62-4.38$ ⑩$2.8×0.37+2.8×0.23$

①
$3.1×0.3×0.5$
$=0.93×0.5$
$=0.465$
②
$0.4×0.7-0.15$
$=0.28-0.15$
$=0.13$
③
$0.25×9×0.4$
$=0.25×0.4×9$
$=0.1×9$
$=0.9$
④
$0.6×0.4×100$
$=0.24×100$
$=24$
⑤
$12×5.62-4.38$
$=67.44-4.38$
$=63.06$
⑥
$4×3.6-2.6$
$=14.4-2.6$
$=11.8$
⑦
$9.6×1.25×80$
$=9.6×(1.25×80)$
$=9.6×100$
$=960$
⑧
$50×1.45×0.02$
$=50×0.02×1.45$
$=1×1.45$
$=1.45$
⑨
$7.5×2.4-7.5×0.4$
$=7.5×(2.4-0.4)$
$=7.5×2$
$=15$
⑩
$2.8×0.37+2.8×0.23$
$=2.8×(0.37+0.23)$
$=2.8×0.6$
$=1.68$

4. 用竖式计算。
①$2.5×1.4=$
④$4.15×2.2=$
⑦$1.08×4.5=$
②$3.6×0.8=$
⑤$0.38×0.6=$
⑧$7.9×0.12=$
③$0.72×45=$
⑥$6.4×0.35=$
⑨$5.25×0.42=$

①
```
2.5
×1.4
----
100
25
----
3.50
```
$2.5×1.4=3.5$
②
```
3.6
×0.8
----
2.88
```
$3.6×0.8=2.88$
③
```
0.72
× 45
------
360
288
------
32.40
```
$0.72×45=32.4$
④
```
4.15
× 2.2
-------
830
830
-------
9.130
```
$4.15×2.2=9.13$
⑤
```
0.38
× 0.6
-------
0.228
```
$0.38×0.6=0.228$
⑥
```
6.4
×0.35
------
320
192
------
2.240
```
$6.4×0.35=2.24$
⑦
```
1.08
× 4.5
-------
540
432
-------
4.860
```
$1.08×4.5=4.86$
⑧
```
7.9
×0.12
------
158
79
------
0.948
```
$7.9×0.12=0.948$
⑨
```
5.25
×0.42
------
1050
2100
------
2.2050
```
$5.25×0.42=2.205$