一、口算。
$27 + 45 =$
$60 ÷ 3 =$
$64 - 15 =$
$64 × 2 =$
$8 × 43 =$
$84 ÷ 3 =$
$400 × 9 =$
$246 ÷ 3 =$
$50 × 71 =$
$370 - 80 =$
$107 × 7 =$
$484 ÷ 4 =$
$40 × 12 =$
$128 + 36 =$
$150 × 2 =$
$832 ÷ 4 =$
$36 × 40 =$
$987 ÷ 7 =$
$\frac{3}{4} - \frac{2}{4} =$
$\frac{2}{9} + \frac{5}{9} =$
$\frac{5}{6} - \frac{1}{6} =$
$\frac{1}{10} + \frac{7}{10} =$
$\frac{2}{5} + \frac{2}{5} =$
$\frac{1}{7} + \frac{5}{7} =$

一、72 20 49
128 344 28
3600 82 3550
290 749 121
480 164 300
208 1440 141
$\frac{1}{4} \frac{7}{9} \frac{4}{6}$
$\frac{8}{10} \frac{4}{5} \frac{6}{7}$

二、用竖式计算，带$*$的要验算。
$58 × 40$
$45 × 12$
$* 28 × 32$
$49 × 27$
$33 × 74$
$* 35 × 68$

二、2320 540 896
1323 2442 2380

```
58
× 40
----
2320
45
× 12
----
90
45
----
540
28
× 32
----
56
84
----
896
验算：
32
× 28
----
256
64
----
896
49
× 27
----
343
98
----
1323
33
× 74
----
132
231
----
2442
35
× 68
----
280
210
----
2380
验算：
68
× 35
----
340
204
----
2380
```