1. 直接写得数。
$2.5×4= $
$2.83×1.01= $
$12.4+7.6= $
$0.3×0.1= $
$2.58+0.2= $
$1.87×0= $
$9×2.5+2.5= $
$4.8×0.2×0.5= $
$0.25×8= $

1. 10
2. 2.8583
3. 20
4. 0.03
5. 2.78
6. 0
7. 25
8. 0.48
9. 2

2. 列竖式计算。(带 * 的得数保留两位小数。)
$6.05×3.8= $
$8.05×3.9= $
$*9.63×0.87= $

①$6.05 × 3.8$的竖式计算：
$\begin{array}{r r r}&&&&6.&0&5\\ ×&&&&&3.&8 \\ \hline &&&4&8&4&0\\ &&1&8&1&5\\ \hline &&2&2.&9&9&0\end{array}$
所以，$6.05 × 3.8 = 22.99$。
②$8.05 × 3.9$的竖式计算：
$\begin{array}{r r r}&&&&8.&0&5\\ ×&&&&&3.&9 \\ \hline &&&7&2&4&5\\ &&2&4&1&5\\ \hline &&3&1.&3&9&5\end{array}$
所以，$8.05 × 3.9 = 31.395$。
③$9.63 × 0.87$的竖式计算：
$\begin{array}{r r r}&&&&9.&6&3\\ ×&&&&&0.&8&7 \\ \hline &&&6&7&4&1\\ &&7&7&0&4\\ \hline &&8.&3&7&8&1\end{array}$
$8.3781 \approx 8.38$（保留两位小数）。
所以，$9.63 × 0.87 \approx 8.38$。

3. 怎样简便就怎样算。
$3.7×1.4×0.05$
$7.6×1.25+1.25×2.4$
$20.06-8.06×2.4$
$9.9×8.3$
$72×0.81+10.4$
$0.27×9.9+0.027$

3.7×1.4×0.05
=3.7×(1.4×0.05)
=3.7×0.07
=0.259
7.6×1.25+1.25×2.4
=1.25×(7.6+2.4)
=1.25×10
=12.5
20.06-8.06×2.4
=20.06-19.344
=0.716
9.9×8.3
=(10-0.1)×8.3
=10×8.3-0.1×8.3
=83-0.83
=82.17
72×0.81+10.4
=58.32+10.4
=68.72
0.27×9.9+0.027
=0.27×9.9+0.27×0.1
=0.27×(9.9+0.1)
=0.27×10
=2.7