Question

简便计算0,9+9,9+99,9+999,9+9999,9 这道题怎么算啊,

Answer 1

0.9+9.9+99.9+999.9+9999.9

=(1-0.1)+(10-0.1)+(100-0.1)+(1000-0.1)+(10000-0.1)

=(1+10+100+1000+10000)-0.5

=11111-0.5

=11110.5