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題目要求用32.12

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乘以0.5

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00:00:06,980 --> 00:00:10,620
小數相乘的時候

4
00:00:10,620 --> 00:00:12,630
跟整數相乘的方法

5
00:00:12,630 --> 00:00:15,700
是一樣的

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00:00:15,700 --> 00:00:18,380
然後數一數兩個小數

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的小數部分

8
00:00:21,330 --> 00:00:23,720
加起來有幾位

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00:00:23,720 --> 00:00:25,340
得數就有幾位小數

10
00:00:25,340 --> 00:00:27,320
下面我來給大家示範一下

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這兩個數要相乘

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00:00:35,720 --> 00:00:38,670
32.12乘以0.5

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00:00:38,670 --> 00:00:39,710
寫算式的時候

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右邊對齊即可

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小數點這時候可以先忽略

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該寫在哪就寫在哪

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可以看成是3212乘以5

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00:00:51,580 --> 00:00:52,920
小數點的問題算完再說

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下面來算一下

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5乘以3212的話

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5・2=10

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進1

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5・1=5 5+1=6

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5・2=10

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進1

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最後5・3=15 15+1=16

27
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這樣就乘完了

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這個數看成05的話

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0就不用乘了

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乘也會得到0

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5乘以3212就得到這個數

32
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下面來看小數的問題

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數一數兩個乘數一共有幾位小數

34
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小數點後

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一共有幾位

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1 2 3 有3位

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兩個數小數點後

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一共有3位小數

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所以最後的答案

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也要有三位小數

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從右向左1 2 3 小數點在這裡

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所以32.12乘以0.5得16.060

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最後這個0也可以不要

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並不改變小數的值

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可以寫成16.06

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那麽最後還要檢查一下

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是不是做的對

48
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上邊這個數大約是32

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乘以0.5

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0.5就是5/10

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也就是1/2

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所以實際上是32.12乘以1/2

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就是求32.12的一半是多少

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32的一半是16 0.12的一半是0.06

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結果非常正確