一、口算。
$15 - 8 =$
$44 + 4 =$
$53 + 8 - 20 =$
$40 + 10 =$
$66 - 5 =$
$24 - 5 + 20 =$
$81 - 8 =$
$77 + 6 =$
$66 - 16 + 40 =$
$18 + 7 =$
$90 - 60 =$
$22 - 11 - 2 =$
$32 - 8 =$
$46 + 7 =$
$48 - 25 + 7 =$
$36 + 4 =$
$76 - 62 =$
$62 - 30 + 8 =$
$85 - 33 =$
$26 + 22 =$
$13 + 25 + 30 =$
$21 + 18 =$
$81 - 61 =$
$80 - 20 - 8 =$
$35 + 12 =$
$88 - 66 =$
$33 + 11 - 4 =$
$49 - 18 =$
$56 + 13 =$
$77 - 25 + 30 =$

1.7
2.48
3.41
4.50
5.61
6.39
7.73
8.83
9.90
10.25
11.30
12.9
13.24
14.53
15.30
16.40
17.14
18.40
19.52
20.48
21.68
22.39
23.20
24.52
25.47
26.22
27.40
28.31
29.69
30.82

二、连一连。