1
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珍奈爾正在爲公路賽訓練

2
00:00:02,710 --> 00:00:06,000
她的計步器記錄了每天她跑的距離

3
00:00:06,000 --> 00:00:08,510
這是她四天來計步器的讀數：

4
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周六 3.89英裏 周日 5.1英裏

5
00:00:13,010 --> 00:00:18,010
周一 10.21英裏 周二 3.35英裏

6
00:00:18,010 --> 00:00:21,860
估算四天來她跑的裏程數

7
00:00:21,860 --> 00:00:23,710
然後計算出準確數值

8
00:00:23,710 --> 00:00:25,130
先來估算一下

9
00:00:25,130 --> 00:00:27,410
我就把它們都四捨五入取整

10
00:00:27,410 --> 00:00:30,320
3.89 約等於4英裏

11
00:00:30,320 --> 00:00:32,120
因爲十分位上

12
00:00:32,120 --> 00:00:34,510
是8 大於5

13
00:00:34,510 --> 00:00:38,230
所以大約就等於4英裏

14
00:00:38,230 --> 00:00:39,930
然後看5.1

15
00:00:39,930 --> 00:00:43,000
因爲1少於5 所以要下舍

16
00:00:43,000 --> 00:00:45,030
近似爲5英裏

17
00:00:45,030 --> 00:00:51,920
10.21 因爲2少於5

18
00:00:51,920 --> 00:00:53,410
要下舍到5英裏

19
00:00:53,410 --> 00:00:55,990
3.35 近似爲3英裏

20
00:00:55,990 --> 00:00:58,720
因爲3比5小 還是要下舍

21
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近似成3英裏

22
00:01:00,490 --> 00:01:04,000
如果加起來的話 4+5=9

23
00:01:04,000 --> 00:01:07,010
9+10=19

24
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19+3=22

25
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所以我的估算結果是4天來她跑了22英裏

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這是我的估算結果

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下面來計算一下準確數值

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向下拖動點

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3.89+5.1--

30
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在小數相加的時候一定要注意

31
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要把小數點對齊

32
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10.21+3.35

33
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把這些都加起來

34
00:01:47,090 --> 00:01:52,050
先看百分位

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第二個數沒有百分位 所以9+0+1=10

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10+5=15

37
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寫5 進1

38
00:02:04,810 --> 00:02:06,450
換個顏色

39
00:02:06,450 --> 00:02:10,000
1+8=9

40
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9+1=10

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10+2=12

42
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12+3=15

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寫5

44
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進1

45
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1+3=4

46
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4+5=9

47
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9+0=9

48
00:02:26,710 --> 00:02:33,040
9+3=12

49
00:02:33,040 --> 00:02:34,050
寫2

50
00:02:34,050 --> 00:02:35,080
進1

51
00:02:35,080 --> 00:02:37,150
進位寫在上邊

52
00:02:37,150 --> 00:02:39,040
不要誤認爲是這些加數的一部分

53
00:02:39,040 --> 00:02:42,030
然後1+1=2

54
00:02:42,030 --> 00:02:43,850
還要注意

55
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這裡是小數點

56
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所以她跑過的準確距離是22.55英裏

57
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我們的估算還是比較接近的

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22英裏

59
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跟準確值非常接近

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誤差比半英裏多一點