1
00:00:00,070 --> 00:00:04,620
计算23・44

2
00:00:04,620 --> 00:00:06,260
或许这个问题最难的

3
00:00:06,260 --> 00:00:07,340
或者说第一个很难的地方

4
00:00:07,340 --> 00:00:10,860
就是要知道这个・代表的是乘法运算

5
00:00:10,860 --> 00:00:15,390
这也可以写成23×44

6
00:00:15,390 --> 00:00:20,750
或者(23)(44)

7
00:00:20,750 --> 00:00:22,470
只要两个括号挨着

8
00:00:22,470 --> 00:00:24,620
就可以代表乘法

9
00:00:24,620 --> 00:00:26,170
那么现在已经知道是要做乘法

10
00:00:26,170 --> 00:00:28,620
下面就着手来运算

11
00:00:28,620 --> 00:00:30,740
是要用23乘以--

12
00:00:30,740 --> 00:00:32,180
我写的大一点

13
00:00:32,180 --> 00:00:36,000
23乘以44

14
00:00:36,000 --> 00:00:38,030
乘法号×写在这里

15
00:00:38,030 --> 00:00:40,070
标明是在做乘法

16
00:00:40,070 --> 00:00:42,110
要注意这种两数垂直做乘法运算的时候

17
00:00:42,110 --> 00:00:44,880
一般是不用点乘号・的

18
00:00:44,880 --> 00:00:48,010
下面开始运算

19
00:00:48,010 --> 00:00:50,680
首先要用个位上的4

20
00:00:50,680 --> 00:00:53,030
乘以23

21
00:00:53,030 --> 00:00:56,520
3×4=12

22
00:00:56,520 --> 00:00:59,630
把2写在个位

23
00:00:59,630 --> 00:01:01,650
但是这一步有一个1的进位

24
00:01:01,650 --> 00:01:04,150
或者说需要把1加到十位

25
00:01:04,150 --> 00:01:07,030
得到12以后 把1写在这里代表进位

26
00:01:07,030 --> 00:01:14,040
4×2=8 8+1=9

27
00:01:14,040 --> 00:01:16,230
所以可以看成是4--

28
00:01:16,230 --> 00:01:20,940
这个4 乘以23得92

29
00:01:20,940 --> 00:01:23,000
这是刚刚算出来的

30
00:01:23,000 --> 00:01:26,050
接下来要算十位上的4乘以23等于多少

31
00:01:26,050 --> 00:01:27,620
那么

32
00:01:27,620 --> 00:01:29,200
在机械地学习这些步骤时

33
00:01:29,200 --> 00:01:30,550
在学习这些步骤时

34
00:01:30,550 --> 00:01:32,000
在这填个0

35
00:01:32,000 --> 00:01:34,010
而之所以放个0

36
00:01:34,010 --> 00:01:37,020
是因为这个4是在十位上

37
00:01:37,020 --> 00:01:38,090
如果还有别的--

38
00:01:38,090 --> 00:01:39,660
在更高位上有个3或者4或者什么

39
00:01:39,660 --> 00:01:41,610
如果是在百位上

40
00:01:41,610 --> 00:01:43,140
这0还要加一个

41
00:01:43,140 --> 00:01:47,150
因为4×23=92

42
00:01:47,150 --> 00:01:47,790
这个刚刚算过了

43
00:01:47,790 --> 00:01:50,770
如果只把4和23再乘一遍

44
00:01:50,770 --> 00:01:52,100
还是会得到92

45
00:01:52,100 --> 00:01:54,450
但这个4其实是40

46
00:01:54,450 --> 00:01:56,590
所以得数应该是920

47
00:01:56,590 --> 00:01:57,920
所以要在这里添个0

48
00:01:57,920 --> 00:01:59,040
大家马上就会明白了

49
00:01:59,040 --> 00:02:01,950
我换一种颜色接着做

50
00:02:01,950 --> 00:02:04,040
现在要乘这个4

51
00:02:04,040 --> 00:02:06,070
4×3=12

52
00:02:06,070 --> 00:02:09,010
2写在这里

53
00:02:09,010 --> 00:02:10,530
在十位上

54
00:02:10,530 --> 00:02:12,160
因为这其实是40×3

55
00:02:12,160 --> 00:02:12,920
想想看

56
00:02:12,920 --> 00:02:14,010
或者思考一下实际的过程

57
00:02:14,010 --> 00:02:15,440
这个2的下一位是没有数的

58
00:02:15,440 --> 00:02:17,040
4×3=12

59
00:02:17,040 --> 00:02:18,240
进位1

60
00:02:18,240 --> 00:02:20,440
这个蓝色的1是上一次的进位

61
00:02:20,440 --> 00:02:21,480
现在就不要管了

62
00:02:21,480 --> 00:02:23,040
不要和现在混了

63
00:02:23,040 --> 00:02:25,010
那是运算个位上的4的时候的进位

64
00:02:25,010 --> 00:02:30,090
然后4×2=8 8+1=9

65
00:02:30,090 --> 00:02:35,230
已经求过了4×23=92

66
00:02:35,230 --> 00:02:40,330
但是这个绿色的4乘以23就是920

67
00:02:40,330 --> 00:02:42,990
因为绿色的4其实是40

68
00:02:42,990 --> 00:02:44,060
这个4在十位上

69
00:02:44,060 --> 00:02:47,580
那么在计算44×23时

70
00:02:47,580 --> 00:02:50,750
就是4×23=92

71
00:02:50,750 --> 00:02:54,500
+40×23=920

72
00:02:54,500 --> 00:02:56,030
说这么多是为了让大家能理解

73
00:02:56,030 --> 00:02:57,050
每一步都是什么意思

74
00:02:57,050 --> 00:02:59,490
最后把两个得数相加就可以了

75
00:02:59,490 --> 00:03:01,000
加起来

76
00:03:01,000 --> 00:03:03,010
2+0=2

77
00:03:03,010 --> 00:03:05,910
9+2=11

78
00:03:05,910 --> 00:03:07,000
进位1

79
00:03:07,000 --> 00:03:09,030
1+9=10

80
00:03:09,030 --> 00:03:11,340
为了好读这里写个逗号

81
00:03:11,340 --> 00:03:12,240
每三位要写一个逗号

82
00:03:12,240 --> 00:03:16,230
最后得23×44=1012