580/[(1-百分之70)X(1-百分之70)]
=580÷(0.3×0.3)
=58000÷9
=54000÷9+4000÷9
=6000+3600÷9+400÷9
=6000+400+360÷9+40÷9
=6400+40+36÷9+4÷9
=6444又9分之4
580/[(1-百分之70)X(1-百分之70)]
=580÷(0.3×0.3)
=58000÷9
=54000÷9+4000÷9
=6000+3600÷9+400÷9
=6000+400+360÷9+40÷9
=6400+40+36÷9+4÷9
=6444又9分之4