用简便方法计算:0.9+0.99+…+0.999999999.

问题描述:

用简便方法计算:0.9+0.99+…+0.999999999.

0.9+0.99+…+0.999999999
=(1-0.1)+(1-0.01)+…+(1-0.000000001)
=9-0.111111111
=8.888888889