Question

0.9 9.9 99.9的简便计算 0.9×9.9×99.9的简便计算。

Answer 1

=(1-0.1)*(10-0.1)*(100-0.1)
=1*10*100-1*100-0.1*100+0.1^2*100-10*0.1+1*0.1+0.1^2-0.1^3
=890.109
技巧就是学会“拆”,