Question

A=0.5+0.55+0.555+.+0.55（10个五）,求A的整数部分.

Answer 1

A=10*0.5+9*0.05+...+1*0.0000000005

0.1A= 10*0.05+9*0.005+...+2*0.0000000005+1*0.00000000005

-0.9A=-10*0.5+1*0.05+...+1*0.00000000005

等比数列求和