WEBVTT

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下面來做等級四的乘法運算

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來看一些例題

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用235乘以--

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用兩種不同顏色來表示

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換顏色的時候大家可能要稍微等一下

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235乘以47

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做等級四的題目

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就跟做等級三的方法是一樣的

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一開始也是用這個7

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乘以235

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7×5=35 進3

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7×3=21

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加上之前的進位3 得24 進2

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7×2=14

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再加上進位2

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得16

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7就乘完了

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然後要乘這個4

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但4是在十位上

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所以要在下邊加一個0

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大家可以這麽看

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乘235的

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不是4 而是40

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所以要填一個0

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但是在寫了0以後

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就可以看成是乘4來運算了

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4×5=20 進2

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把上一步的進位劃掉

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4×3=12

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加上進上來的2

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得14 進1

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4×2=8

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加上進位1

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得9

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現在把兩個乘積加起來

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5+0=5

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4+0=4

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6+4=10 進1

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1+1+9 得11

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所以結果是11045

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再做一道

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用873乘以--

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我是在臨時湊數

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所以比較慢--

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873乘以--找個大數--

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9--個位十位我用不同的顏色寫

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這樣大家就能更好理解

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我說的是什麽意思了

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乘以97

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剛用過7了

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就98吧

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就跟之前的步驟一樣 先看個位

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也就是8

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8×873

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8×3=24

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進2

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8×7=56

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56+2=58

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進5

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8×8=64

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加上剛進的5

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就是69

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8就乘完了

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接下來乘9

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或者說

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是873乘以90

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但是乘以90就是

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乘以9--

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後邊再加個0

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所以在這寫個0

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然後9×3=27 進2

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忘了要先劃掉這些進位了

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把之前寫的都劃掉

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9×3=27

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進2

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9×7=63

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加上進位2 是65

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進6

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9×8=72

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加上進位6

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是78

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然後再做加法

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個位是4 8+7=15 進1

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1+9+5=15 進1

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1+6+8還是15 進1

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1+7=8

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手邊又沒有計算器--

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如果我沒算錯的話--

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如果沒有粗心計算錯誤

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那麽答案是85554

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再做一道

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這道題能清楚闡釋我要說的內容

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下一道題

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差不多是等級五的內容

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因爲我要寫的是

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兩個三位數相乘

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但其實道理是一樣的

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希望大家能夠發現運算的規律

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那麽 234乘以--

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現在要用三種顏色來寫了

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643

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首先來算個位的3

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8×234

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3×4=12 進1

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3×3=9 9+1

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得10 進1

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3×2=6 6+1

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得7

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個位就做完了

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我覺得哪裏做錯了 來看一下

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3×4=12--