一、口算。
$3×25=$
$640-70=$
$50+605=$
$74×3=$
$23×6=$
$322-92=$
$2×53=$
$107×5=$
$4×300=$
$15×3=$
$470+230=$
$408×2=$
$63×3=$
$300×3=$
$5×800=$
$75×5=$
$11×8=$
$202×7=$
$306×3=$
$87×3=$
$120×6=$
$27×9=$
$130-90=$
$240×3=$

1.75
2.570
3.655
4.222
5.138
6.230
7.106
8.535
9.1200
10.45
11.700
12.816
13.189
14.900
15.4000
16.375
17.88
18.1414
19.918
20.261
21.720
22.243
23.40
24.720

二、计算下面各题。
$86×6 - 312$
$176 + 99÷9$
$7×(543 - 506)$
$123 + 4×123$
$(668 - 596)÷9$
$(361 - 353)×305$

1.204
2.187
3.259
4.615
5.8
6.2440