四則運算的原本 ⑹

⑹ + - × ÷ 的原本
   ÷ 是 - 的速算法，與 × 相反互逆
   ÷ × 互為逆運算，如 + - 是逆運算
          +   ⇄   -
          ↯          ↯
          ×   ⇄   ÷
   16 + □ = 33   ,  □ = 33  - 16 = 17
   ○  -  28 = 45  ,  ○ = 45 + 28 = 73
   19 × ☆= 57  ,  ☆ = 57 ÷ 19 =  3
   ◇  ÷ 15 =   8  ,  ◇ = 8 × 15 = 120
   除法是減法延伸,減法不適合交換
   除法也不適合交換。加,乘則皆可
   6+6+6=6×3    乘是加的速算
   5+9=9+5         ∵加適合交換律
   9×5=5×9         ∴乘也適合
   10顆糖分二盤,每盤幾顆糖？
         10  - (  ) - (  ) = 0
     ∵10  ÷ 2 = (  )
     ∴減法的速算是除法
    65人分座五台車,每車幾人？
         65  -□ -□ -□ -□ -□ = 0
         65 = □ × 5 ,  □ = 65 ÷ 5 =13

   ⑹ + - × ÷ the original
   ÷ is - the speed algorithm, and × opposite the inverse
   ÷ × mutually inverse operation, such as + - is the inverse operation
          +   ⇄   -
          ↯          ↯
          ×   ⇄   ÷
   16 + □ = 33, □ = 33 - 16 = 17
   ○ - 28 = 45, ○ = 45 + 28 = 73
   19 × ☆ = 57, ☆ = 57 ÷ 19 = 3
   ◇ ÷ 15 = 8, ◇ = 8 × 15 = 120
   Division is a subtraction extension, subtraction is not suitable for exchange
   Division is not suitable for exchange. Plus, multiplication can be
   6 + 6 + 6 = 6 × 3 multiplication is the speed of the operator
   5 + 9 = 9 + 5 ∵ add the appropriate exchange law
   9 × 5 = 5 × 9 ∴ multiplication is also suitable
   10 candy two sets, each few sugar a few?
         10 - () - () = 0
     ∵ 10 ÷ 2 = ()
     ∴ subtraction of the speed is divided
    65 seats five cars, several people per car?
         65 - □ - □ - □ - □ - □ = 0
         65 = □ x 5, □ = 65 ÷ 5 = 13