1. 直接写出得数。
$8 + 3.3 =$ $18×70 =$ $70÷70 =$
$4.2 - 1.8 =$ $2.4 - 1.2 =$ $4.2 - 2.9 =$
$1.7 + 3.2 =$ $10 - 5.1 =$ $5.2 - 2.6 =$
$9.1 - 1.92 =$ $35×20 =$ $220÷20 =$
$88÷44 =$ $93.5 - 87.8 =$ $6.6 + 3.35 =$
$0.5 + 6.3 =$ $2.3 + 3.2 =$ $4.56 - 0.23 =$
$2.13 + 0.5 =$ $45.01 + 23.9 =$ $5.68 - 4.6 =$
$22.4 + 15.36 =$ $46.9 - 12.8 =$ $0.1×10 =$

$8 + 3.3 = 11.3$
$18×70 = 1260$
$70÷70 = 1$
$4.2 - 1.8 = 2.4$
$2.4 - 1.2 = 1.2$
$4.2 - 2.9 = 1.3$
$1.7 + 3.2 = 4.9$
$10 - 5.1 = 4.9$
$5.2 - 2.6 = 2.6$
$9.1 - 1.92 = 7.18$
$35×20 = 700$
$220÷20 = 11$
$88÷44 = 2$
$93.5 - 87.8 = 5.7$
$6.6 + 3.35 = 9.95$
$0.5 + 6.3 = 6.8$
$2.3 + 3.2 = 5.5$
$4.56 - 0.23 = 4.33$
$2.13 + 0.5 = 2.63$
$45.01 + 23.9 = 68.91$
$5.68 - 4.6 = 1.08$
$22.4 + 15.36 = 37.76$
$46.9 - 12.8 = 34.1$
$0.1×10 = 1$

2. 判断，对的画“√”，错的画“×”。
(1)7.65 这个小数是由 7 个 1、6 个 0.1 和 5 个 0.01 组成的。 ()
(2)小数的位数越多，小数越大。 ………………………………()
(3)计算小数加减法时，要像计算整数加减法那样把末位对齐。()
(4)小数部分最大的计数单位是$\frac{1}{10}$。 ……………………………()
(5)小数点的后面添上 0 或去掉 0，小数的大小不变。 ………()

(1) √
(2) ×
(3) ×
(4) √
(5) ×

3. 列竖式计算。
$8.6 + 4.5 =$ $7.9 + 6.6 =$ $8.7 - 1.8 =$
$10 - 5.69 =$ $6.41 - 3.7 =$ $7.6 + 12.69 =$

8.6
+ 4.5
------
13.1
$8.6 + 4.5 = 13.1$
7.9
+ 6.6
------
14.5
$7.9 + 6.6 = 14.5$
8.7
1.8
------
6.9
$8.7 - 1.8 = 6.9$
10.00
5.69
-------
4.31
$10 - 5.69 = 4.31$
6.41
3.70
------
2.71
$6.41 - 3.7 = 2.71$
7.60
+12.69
------
20.29
$7.6 + 12.69 = 20.29$