一、口算。
$480÷ 40=$
$4× 105=$
$106× 50=$
$202× 6=$
$50× 21=$
$84+21=$
$366÷ 2=$
$300× 4=$
$240-54=$
$16× 300=$
$320+90=$
$50× 24=$
$72-24=$
$302-30=$
$720÷ 3=$
$120÷ 5=$
$620÷ 4=$
$12× 800=$
$50× 90=$
$30× 27=$
$160÷ 4=$
$300÷ 4=$
$640÷ 80=$
$80× 150=$

1.12
2.420
3.5300
4.1212
5.1050
6.105
7.183
8.1200
9.186
10.4800
11.410
12.1200
13.48
14.272
15.240
16.24
17.155
18.9600
19.4500
20.810
21.40
22.75
23.8
24.12000

二、计算下面各题。
$713 - 146 ÷ 73 × 98$ $812 - (278 + 322) ÷ 15$ $[206 - (63 + 72)] × 58$
$29 × 23 - 308 + 68$ $(79 - 26) × (71 + 26)$ $700 ÷ [(205 - 198) × 4]$

1.517
2.772
3.4118
4.427
5.5141
6.25