1
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下面來做等級四的乘法運算

2
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來看一些例題

3
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用235乘以--

4
00:00:10,718 --> 00:00:14,330
用兩種不同顏色來表示

5
00:00:14,330 --> 00:00:21,690
換顏色的時候大家可能要稍微等一下

6
00:00:21,690 --> 00:00:23,498
235乘以47

7
00:00:23,498 --> 00:00:26,960
做等級四的題目

8
00:00:26,960 --> 00:00:31,060
就跟做等級三的方法是一樣的

9
00:00:31,070 --> 00:00:36,165
一開始也是用這個7

10
00:00:36,165 --> 00:00:44,604
乘以235

11
00:00:44,604 --> 00:00:49,750
7×5=35 進3

12
00:00:49,780 --> 00:00:51,030
7×3=21

13
00:00:51,040 --> 00:00:52,560
加上之前的進位3 得24 進2

14
00:00:52,570 --> 00:00:54,390
7×2=14

15
00:00:54,390 --> 00:00:58,240
再加上進位2

16
00:00:58,250 --> 00:01:02,187
得16

17
00:01:02,187 --> 00:01:04,044
7就乘完了

18
00:01:04,044 --> 00:01:06,490
然後要乘這個4

19
00:01:06,500 --> 00:01:09,310
但4是在十位上

20
00:01:09,310 --> 00:01:14,903
所以要在下邊加一個0

21
00:01:14,903 --> 00:01:17,665
大家可以這麽看

22
00:01:17,665 --> 00:01:24,180
乘235的

23
00:01:24,180 --> 00:01:29,800
不是4 而是40

24
00:01:29,810 --> 00:01:32,000
所以要填一個0

25
00:01:32,010 --> 00:01:40,570
但是在寫了0以後

26
00:01:40,570 --> 00:01:43,670
就可以看成是乘4來運算了

27
00:01:43,680 --> 00:01:46,220
4×5=20 進2

28
00:01:46,230 --> 00:01:48,150
把上一步的進位劃掉

29
00:01:48,150 --> 00:01:56,882
4×3=12

30
00:01:56,882 --> 00:02:00,559
加上進上來的2

31
00:02:00,559 --> 00:02:06,085
得14 進1

32
00:02:06,085 --> 00:02:08,082
4×2=8

33
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加上進位1

34
00:02:10,791 --> 00:02:13,110
得9

35
00:02:13,120 --> 00:02:15,165
現在把兩個乘積加起來

36
00:02:15,165 --> 00:02:15,950
5+0=5

37
00:02:15,960 --> 00:02:19,869
4+0=4

38
00:02:19,869 --> 00:02:22,646
6+4=10 進1

39
00:02:22,650 --> 00:02:23,588
1+1+9 得11

40
00:02:23,588 --> 00:02:26,714
所以結果是11045

41
00:02:26,714 --> 00:02:32,070
再做一道

42
00:02:32,080 --> 00:02:40,090
用873乘以--

43
00:02:40,090 --> 00:02:44,400
我是在臨時湊數

44
00:02:44,410 --> 00:02:46,470
所以比較慢--

45
00:02:46,470 --> 00:02:47,570
873乘以--找個大數--

46
00:02:47,580 --> 00:02:49,410
9--個位十位我用不同的顏色寫

47
00:02:49,410 --> 00:02:53,830
這樣大家就能更好理解

48
00:02:53,840 --> 00:02:56,006
我說的是什麽意思了

49
00:02:56,006 --> 00:02:59,310
乘以97

50
00:02:59,310 --> 00:03:02,028
剛用過7了

51
00:03:02,028 --> 00:03:03,525
就98吧

52
00:03:03,525 --> 00:03:06,710
就跟之前的步驟一樣 先看個位

53
00:03:06,710 --> 00:03:12,930
也就是8

54
00:03:12,940 --> 00:03:20,805
8×873

55
00:03:20,805 --> 00:03:22,336
8×3=24

56
00:03:22,352 --> 00:03:25,480
進2

57
00:03:25,490 --> 00:03:28,030
8×7=56

58
00:03:28,030 --> 00:03:29,710
56+2=58

59
00:03:29,710 --> 00:03:36,234
進5

60
00:03:36,234 --> 00:03:42,160
8×8=64

61
00:03:42,160 --> 00:03:45,183
加上剛進的5

62
00:03:45,183 --> 00:03:48,012
就是69

63
00:03:48,012 --> 00:03:50,870
8就乘完了

64
00:03:50,880 --> 00:03:51,900
接下來乘9

65
00:03:51,900 --> 00:03:54,650
或者說

66
00:03:54,660 --> 00:03:55,792
是873乘以90

67
00:03:55,792 --> 00:03:58,220
但是乘以90就是

68
00:03:58,220 --> 00:04:00,595
乘以9--

69
00:04:00,595 --> 00:04:03,770
後邊再加個0

70
00:04:03,770 --> 00:04:10,971
所以在這寫個0

71
00:04:10,971 --> 00:04:13,848
然後9×3=27 進2

72
00:04:13,848 --> 00:04:23,148
忘了要先劃掉這些進位了

73
00:04:23,148 --> 00:04:26,010
把之前寫的都劃掉

74
00:04:26,020 --> 00:04:28,940
9×3=27

75
00:04:28,940 --> 00:04:32,300
進2

76
00:04:32,310 --> 00:04:36,560
9×7=63

77
00:04:36,560 --> 00:04:38,610
加上進位2 是65

78
00:04:38,620 --> 00:04:41,178
進6

79
00:04:41,178 --> 00:04:43,720
9×8=72

80
00:04:43,730 --> 00:04:45,539
加上進位6

81
00:04:45,539 --> 00:04:46,950
是78

82
00:04:46,950 --> 00:04:48,430
然後再做加法

83
00:04:48,430 --> 00:04:50,860
個位是4 8+7=15 進1

84
00:04:50,870 --> 00:04:54,338
1+9+5=15 進1

85
00:04:54,338 --> 00:04:56,430
1+6+8還是15 進1

86
00:04:56,430 --> 00:04:58,564
1+7=8

87
00:04:58,564 --> 00:05:03,018
手邊又沒有計算器--

88
00:05:03,018 --> 00:05:04,386
如果我沒算錯的話--

89
00:05:04,386 --> 00:05:06,134
如果沒有粗心計算錯誤

90
00:05:06,134 --> 00:05:08,393
那麽答案是85554

91
00:05:08,393 --> 00:05:12,135
再做一道

92
00:05:12,135 --> 00:05:19,120
這道題能清楚闡釋我要說的內容

93
00:05:19,120 --> 00:05:23,670
下一道題

94
00:05:23,680 --> 00:05:25,468
差不多是等級五的內容

95
00:05:25,468 --> 00:05:26,500
因爲我要寫的是

96
00:05:26,510 --> 00:05:29,354
兩個三位數相乘

97
00:05:29,404 --> 00:05:32,874
但其實道理是一樣的

98
00:05:32,874 --> 00:05:34,355
希望大家能夠發現運算的規律

99
00:05:34,355 --> 00:05:37,177
那麽 234乘以--

100
00:05:37,177 --> 00:05:41,220
現在要用三種顏色來寫了

101
00:05:41,220 --> 00:05:47,490
643

102
00:05:47,500 --> 00:05:52,700
首先來算個位的3

103
00:05:52,700 --> 00:05:55,460
8×234

104
00:05:55,470 --> 00:05:59,670
3×4=12 進1

105
00:05:59,680 --> 00:06:02,258
3×3=9 9+1

106
00:06:02,258 --> 00:06:04,228
得10 進1

107
00:06:04,228 --> 00:06:05,469
3×2=6 6+1

108
00:06:05,469 --> 00:06:07,370
得7

109
00:06:07,378 --> 00:06:09,601
個位就做完了

110
00:06:09,601 --> 00:06:13,690
我覺得哪裏做錯了 來看一下

111
00:06:13,690 --> 00:06:16,958
3×4=12--