最好看的战争大片:脑算除法第3讲

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脑算除法第1讲


补数除法,有3种;

1、稍小于一百的除补数求商(加除法):从被除数首位起,逐位与除数补数乘加,够一个除数就是补商,保留小数两位。

   补数 043                                 补数01                              补数 03

446919÷957=467                        326÷99=3.29                      453÷97=4.67

+172   4×043                +03    3×01             +12   4×03

464119                       329                     465

 +258   6×043                +02    2×01             +18    6×03

466699                       3292                    4668

  +258    6×043                +09    9×01            +18    6×03

466957                       32929                   46698

  -957 9571                                      97  97

467                                                  46701   

 

2、稍大于一百除补数求商(减除法):从被除数首位起,逐位与除数超补数乘减,不够减退商,保留小数两位。

         补数02                                  补数03

      356÷102=3.49                        782÷103=7.59

     06  3×02                 -21   7×03

      350   不够减5                  761    不够减65

       -08   4×02                -15   5×03   

      3492                       7595

        -18   9×02                -27   9×03

      34902                      75923

 

3、补数求商,加减混合除法:

 补数 212                           补数 21

      788÷198=156024              7189÷79=91

             +424   2×212        +147   7×21

           424   2×212           165   147+18=1582

           156024                 158     2×79  

                                     79    7+29

                                     79     11

                                             91         

 脑算除法第2讲


利用4个阿拉伯数字编写顺口溜儿歌(口诀),便于掌握,不假思索,张口就来,方便适用。

被除数                                 

除  数         带有底线的,共有16句必须牢记,            4

         2150    掌握顺口溜是怎样形成的,现编就行。    除 被 商 

         3131  3262  利用珠算单归口诀转变                 

     4122  4250  4372                              数 数 数 

     5120  5240  5360  5480                        6÷8=0.70.4

     6114  6232  6350  6464  6582                   8×0.7+0.4=6

     7113  7226  7342  7455  7571  7684

     8112  8224  8336  8450  8562  8674  8786

     9111  9222  9333  9444  9555  9666  9777  9888 

史丰收速算法主要是个位律和进位律就是本个加后进

个位律:本个就是两个一位数相乘的个位数。如:3×7=21个位数是1

1乘,任何数其积不变  123456789

2乘,自身加倍只记个          246802468

3乘,偶补倍奇补倍加        369258147

4乘,偶补奇凑515           482604826

5乘,偶0                505050505

6乘,偶自身奇±             628406284

7乘,偶自倍奇倍加          741852963

8乘,被乘数加倍的个位补数     864208642

9乘,偶奇均为自身补           987654321

进位律:后进就是提前从后面进上来的数

1/2=0.551

1/3=0.3312/3=0.6662

1/4=0.252512/4=0.5523/4=0.75753

1/5=0.2212/5=0.4423/5=0.6634/5=0.884

1/6=0.161612/6=0.3323/6=0.5534/6=0.664

    5/6=0.83835

1/714285712/728571423/742857134/75714284

    5/771428556/78571426

1/8=0.12512512/8=0.252523/8=0.37537534/8=0.554

5/8=0.62562556/8=0.757567/8=0.8758757

1/9=0.1112/9=0.2223/9=0.3334/9=0.444

     5/9=0.5556/9=0.6667/9=0.7778/9=0.888

例题:

3/2=1.54/3=1.3335/3=2.66629/3=9.6665/4=1.257/4=1.75438/4=109.5

6/5=1.27/5=1.47/6=1.66611/6=1.8338/7=1.14285718/7=1.8571429/8=1.125

11/8=1.37513/8=1.62582/9=9.11164/9=7.11158/9=6.44483/9=9.222

     脑算除法第3讲


斤两口诀的利用(原1斤是16两)

                        16       32        64        128 

   05    025   0125      00625      003125      0015625     00078125

        05   025       0125        00625        003125       0015625

         075   0375      01875           

             05        025

               0625      03125

               075       0375 1/16=0.0625

                       04375

   1/2=0.5               05      1/32=0.03125

       1/4=0.25          05625            1/64=0.015625

           1/8=0.125     0625                      1/128=0.0078125

                       十一06875

                       十二075

                       十三08125

                       十四0875

                       十五09375

                       十六

1、一退625的利用:任何数乘625就把625看作1,如625×831×83÷1653两。5斤是积的前段数,3两是积的后段数1875.51875

2、二125的利用:任何数乘125就把125看作2,如125×482×48÷1660两=6000

3、三1875的利用:任何数乘1875就把1875看作3,如1875×493×49÷1693两=91875

    4、五3125的利用:任何数乘3125就把3125看作5,如3125×675×67÷162015两=209375

    5、六375的利用:任何数乘375就把375看作6,如375×876×87÷163210两=32625

    6、七4375的利用:任何数乘4375就把4375看作7,如4375×837×83÷16365两=363125

    7、九5625的利用:任何数乘5625就把5625看作9,如5625×789×78÷164314两=438750

    8、十一6875的利用:任何数乘6875就把6875看作11,如6875×5911×59÷16409两=405625。 

    9、十三8125的利用:任何数乘8125就把8125看作13,如8125×4913×49÷163913两=398125

   10、十四875的利用:任何数乘875就把875看作14,如875×6814×68÷16598两=59500

   11、十五9375的利用:任何数乘9375就把9375看作15,如9375×8915×89÷16837两=834375