屋面光伏支架水泥墩:脑算乘法第57讲

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脑算乘法第57讲

(2009-04-12 15:23:52)转载 标签:

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脑算乘法第57讲

前两位数相同,尾不和10的两个三位数相乘:前两位平方,连上尾数相乘的积,加上前两位乘尾数的积。

    564×561=562连4×1+560×(4+1)     

            =313604+2800                                      

            =316404                                                 

    597×594=348128+590×11

            =348128+6490

            =354618

    648×645=642连40+640×13            

            =409640+8320                        

          =417960                                                                               

    484×487=230428+480×11

            =230428+5280

            =235708

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