99.9+O.2+0.9+9.9+0.2+999.9======

99.9+O.2+0.9+9.9+0.2+999.9======
99.9+O.2+0.9+9.9+0.2+999.9
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=
=
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=
=

99.9+O.2+0.9+9.9+0.2+999.9======
99.9+0.2+0.9+9.9+0.2+999.9
=(99.9+0.1)+(0.1+0.9)+(9.9+0.1)+(0.1+999.9)
=100+1+10+1000
=1111

99.9+O.2+0.9+9.9+0.2+999.9
=99.9＋0.1＋0.9＋0.1＋9.9＋0.1＋999.9＋0.1
= 1＋10＋100＋1000
= 1111

1111

99.9+O.2+0.9+9.9+0.2+999.9
= 99.9+(0.1+0.1)+0.9+9.9+(0.1+0.1)+999.9
= (99.9+0.1)+(0.1+0.9)+(9.9+0.1)+(0.1+999.9)
= 100+1+100+1000
= 101+100+1000
= 201+1000
=1201

=99.9+(0.1+0.1)+0.9+9.9+(0.1+0.1)+999.9
=(99.9+0.1)+(0.1+0.9)+(9.9+0.1)+(0.1+999.9)
=101+10+1000
=1111

OK！
原式=（999.9+99.9+9.9+0.9）+（0.2+0.2）
=[（1000+100+10+1）-（0.1+0.1+0.1+0.1）]
+0.4
=[1111-0.4]+0.4
=1111+0
=1111
计算，有时候就是这么简单！

原式=（999.9+99.9+9.9+0.9）+（0.2+0.2）
=[（1000+100+10+1）-（0.1+0.1+0.1+0.1）] +0.4
=[1111-0.4]+0.4
=1111+0
=1111
或
原式=99.9+0.2+0.9+9.9+0.2+999.9
=(99.9+0.1)+(0.1+0.9)+(9.9+0.1)+(0.1+999.9)
=100+1+10+1000
=1111

100+1+10+1000

999.9
+ 99.9
+ 9.9
+ 0.9
+ 0.2
+ 0.2
______________
1111.0

1111

99.9+O.2+0.9+9.9+0.2+999.9
=(99.9+0.1)+(0.1+0.9)+(9.9+0.1)+(0.1+999.9)
=100+1+10+1000
=1111

=99.9+0.1+0.1+0.9+9.9+0.1+0.1+999.9
=(99.9+0.1)+(0.1+0.9)+(9.9+0.1)+(0.1+999.9)
=100+1+10+1000
=1111

99.9+O.2+0.9+9.9+0.2+999.9
=0.1*(999+9+99+9999+2+2)
=0.1*(4+9*111+11+1111)
=0.1*(4+9*1233)
=0.1*11101
=1110.1

=(99.9+0.1)+(0.1+0.9)+(9.9+0.1)+(0.1+999.9)
=100+1+10+1000
=1111

〔99.9+0.1〕+〔0.9+0.1+〕〔9.9+0.1〕+〔999.9+0.1〕
= 100+1+10+1000
=1111

用简便方法啦

99.9+O.2+0.9+9.9+0.2+999.9
= 99.9+(0.1+0.1)+0.9+9.9+(0.1+0.1)+999.9
=(99.9+0.1)+(0.1+0.9)+(9.9+0.1)+(0.1+999.9)
=100++1+10+1000
=1+10+100+1000
=1111

99.9+0.2+0.9+9.9+0.2+999.9
=(100-0.1)+(1-0.8)+(1-0.1)+(10-0.1)+(1-0.8)+(1000-0.1)
=(100+1+1+10+1+1000)+(0.1+0.8+0.1+0.1+0.8+0.1)
=1113+2
=1115