楼上错了是
0.9+0.98+0.997+0.9996+0.99995+0.999994
=(1-0.1)+(1-0.02)+(1-0.003)+(1-0.0004)+(1-0.00005)+(1-0.000006)
=6-(0.1+0.02+0.003+0.0004+0.00005+0.000006)
=6-0.123456
=5.876544