0和0.1中间的数字是:0.05。0和0.1中间的排列顺序数字是:0.01,0.02,0.03,0.04,0.05,0.06,0.07,0.08,0.09
无数个。0.01 0.02 0.03 ...... 0.001 0.0001.....
有无数个小数
对于一个近似数,从左边第一个不是0的数字起,到精确到的位数止,所有的数字都叫做这个数的有效数字 。所以0.1有一位有效数字。