1. 直接写出得数。
$1.9 + 0.5 =$ $1 - 0.09 =$ $0.9 + 0.3 =$
$6.9 - 6 =$ $0.8 + 8 =$ $10 - 5.4 =$
$1 - 0.25 =$ $2.7 - 0.8 =$ $4.5 - 2.6 =$
$17.5 + 5 =$ $9.3 - 3 =$ $2.1 + 8 =$
$0.5 + 0.6 =$ $2.4 + 0.61 =$ $3.7 + 6.3 - 4.7 =$

$1.9 + 0.5 = 2.4$
$1 - 0.09 = 0.91$
$0.9 + 0.3 = 1.2$
$6.9 - 6 = 0.9$
$0.8 + 8 = 8.8$
$10 - 5.4 = 4.6$
$1 - 0.25 = 0.75$
$2.7 - 0.8 = 1.9$
$4.5 - 2.6 = 1.9$
$17.5 + 5 = 22.5$
$9.3 - 3 = 6.3$
$2.1 + 8 = 10.1$
$0.5 + 0.6 = 1.1$
$2.4 + 0.61 = 3.01$
$3.7 + 6.3 - 4.7 = 5.3$

2. 列竖式计算，带★的要验算。
$38.5 + 80.8 =$ $53.5 - 25.6 =$ $10 - 6.79 =$
$70.45 + 29.8 =$ $25.1 - 16.09 =$ ★$45.2 - 16.79 =$

$38.5 + 80.8 = 119.3$
38.5
+ 80.8
------
119.3
$53.5 - 25.6 = 27.9$
53.5
25.6
------
27.9
$10 - 6.79 = 3.21$
10.00
6.79
-------
3.21
$70.45 + 29.8 = 100.25$
70.45
+29.80
------
100.25
$25.1 - 16.09 = 9.01$
25.10
-16.09
------
9.01
★$45.2 - 16.79 = 28.41$
45.20
-16.79
------
28.41
验算：
28.41
+16.79
------
45.20

3. 计算下列各题，能简算的要简算。
$15.73 - (6.25 + 3.73)$ $2.54 + 6.82 + 7.46 - 6.82$
$3.87 + 1.66 + 0.13$ $67.6 - 6.3 - 3.7$
$3.99 + 3.75 + 6.25$ $8.07 - 2.48 - 0.29$

$15.73 - (6.25 + 3.73)$
$=15.73 - 3.73 - 6.25$
$=12 - 6.25$
$=5.75$
$2.54 + 6.82 + 7.46 - 6.82$
$=2.54 + 7.46 + (6.82 - 6.82)$
$=10 + 0$
$=10$
$3.87 + 1.66 + 0.13$
$=3.87 + 0.13 + 1.66$
$=4 + 1.66$
$=5.66$
$67.6 - 6.3 - 3.7$
$=67.6 - (6.3 + 3.7)$
$=67.6 - 10$
$=57.6$
$3.99 + 3.75 + 6.25$
$=3.99 + (3.75 + 6.25)$
$=3.99 + 10$
$=13.99$
$8.07 - 2.48 - 0.29$
$=5.59 - 0.29$
$=5.3$