根据数字的数字进行ROUNDING

我有以下Excel电子表格:

AB 1 6.355 6.000 2 58.690 50.000 3 357.867 350.000 4 1.260.563 1.200.000 5 12.480.370 12.400.000 

列A中,我有一堆radnom数字,每次用户input新的数据到电子表格中都可以改变。

B列中,我想在下面的系统中对列A中的数字进行CUT和ROUNDDOWN:

 Number consists of 4 digits --> CUT and ROUNDDOWN after the 1st digit Number consitst of 5 digits --> CUT and ROUNDDOWN after the 1st digit Number consists of 6 digits --> CUT and ROUNDDOWN after the 2nd digit Number consists of 7 digits --> CUT and ROUNDDOWN after the 2nd digit Number consists of 8 digits --> CUT and ROUNDDOWN after the 3rd digit 

到目前为止,我尝试了以下几点:

 =ROUNDDOWN(A1,1-LEN(A1)) 

但是,这个公式只适用于4-5位数字。 之后,我将不得不将1更改为2 ,依此类推。

有没有办法根据上述系统自动舍入?

将下面的公式B1向下:

 =ROUNDDOWN(A1,-(INT(LOG10(A1)/2)+2))