计算:0.01+0.12+0.23+0.34……0.78+0.89 注意,是循环小数.循环点在最后一位.

0.01+0.12+0.23+0.34……0.78+0.89
=(0.0+0.1+0.2+...+0.8)+(0.0111...+0.0222...+...+0.0999...)
=(0.0+0.1+0.2+...+0.8)+0.0111...*(1+2+...+9)
=0.1*(1+2+...+8)+1/90*(1+2+...+9)
=3.6+1/90*45
=3.6+0.5
=4.1
---------------此为一解-----顶起-----------------
0.01+0.12+0.23+0.34……0.78+0.89
=(0.01+0.78)+（0.12+0.67）+（0.23+0.56）+（0.34+0.45）+0.89
=0.799999999*4+(0.799999999+0.1)
=0.799999999*5+0.1
=(72/90)*5+0.1=4.1