Question

0.9+0.99+0.999+0.9999+0.99999的简便计算方法

Answer 1

0.9+0.99+0.999+0.9999+0.99999
=1-0.1+1-0.01+1-0.001+1-0.0001+1-0.00001
=5-(0.1+0.01+0.001+0.0001+0.00001)
=5-0.11111
=4,88889