1. 直接写出得数。
$1 - 0.9 =$ $0.32 + 2.58 =$ $10.8 + 5.05 =$
$3.11 + 2.22 =$ $0.36 + 0.4 =$ $3.6 + 4.4 =$
$5 - 0.12 =$ $4.3 - 1.6 =$ $0.04 + 0.4 =$
$6.4 + 3.6 =$ $0.9×0.09 =$ $1 - 0.05 =$
$5.7×0.9 =$ $7.3 + 2.7 =$ $0.3 + 0.65 =$

$1 - 0.9 = 0.1$ $0.32 + 2.58 = 2.9$ $10.8 + 5.05 = 15.85$
$3.11 + 2.22 = 5.33$ $0.36 + 0.4 = 0.76$ $3.6 + 4.4 = 8$
$5 - 0.12 = 4.88$ $4.3 - 1.6 = 2.7$ $0.04 + 0.4 = 0.44$
$6.4 + 3.6 = 10$ $0.9×0.09 = 0.081$ $1 - 0.05 = 0.95$
$5.7×0.9 = 5.13$ $7.3 + 2.7 = 10$ $0.3 + 0.65 = 0.95$

2. 列竖式计算。
$0.58 + 0.62 =$ $9 - 0.98 =$ $7.5×8.06 =$

0.58
+ 0.62
------
1.2
$0.58 + 0.62 = 1.2$
9.00
0.98
------
8.02
$9 - 0.98 = 8.02$
8.06
× 7.5
--------
4030
5642
--------
60.45
$7.5×8.06 = 60.45$

3. 计算下列各题，能简算的要简算。
$47.8 - 7.45 + 8.2$ $15.2 - 6.8 - 3.45$
$4.25×9.9 + 42.5$ $2.88×1.43 - 2.88×0.43$

$47.8 - 7.45 + 8.2$
$=47.8 + 8.2 - 7.45$
$=56 - 7.45$
$=48.55$
$15.2 - 6.8 - 3.45$
$=8.4 - 3.45$
$=4.95$
$4.25×9.9 + 42.5$
$=4.25×9.9 + 4.25×10$
$=4.25×(9.9 + 10)$
$=4.25×19.9$
$=4.25×(20 - 0.1)$
$=4.25×20 - 4.25×0.1$
$=85 - 0.425$
$=84.575$
$2.88×1.43 - 2.88×0.43$
$=2.88×(1.43 - 0.43)$
$=2.88×1$
$=2.88$

4. 解方程。
$x + 1.56 = 6.24$ $2x = 302$
$x - 7.6×5 = 18$ $0.9 + 4x = 24.9$

解：$x + 1.56 = 6.24$
$x = 6.24 - 1.56$
$x = 4.68$
解：$2x = 302$
$x = 302÷2$
$x = 151$
解：$x - 7.6×5 = 18$
$x - 38 = 18$
$x = 18 + 38$
$x = 56$
解：$0.9 + 4x = 24.9$
$4x = 24.9 - 0.9$
$4x = 24$
$x = 24÷4$
$x = 6$