9.1+9.2+9.3+9.4+9.1+8.9+8.8
=9+0.1+9+0.2+9+0.3+9+0.4+9+0.1+9-0.1+9-0.2
=9*7+0.1+0.3+0.4
=63+0.8
=63.89为什么×7一共七个9相加。。。。哦哦，谢