答会必踩!
问题描述：
答会必踩!
1.
0.9+0.99+0.999
2.
9999+9998+9997+9996
答
1.
0.9+0.99+0.999
=1-0.1+1-0.01+1-0.001
=3-0.111
=2.889
2.
9999+9998+9997+9996
=10000-1+10000-2+10000-3+10000-4
=40000-10
=39990