简便计算1.9+19.9+199.9-0.4

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简便计算1.9+19.9+199.9-0.4

简便计算1.9+19.9+199.9-0.4
简便计算1.9+19.9+199.9-0.4

简便计算1.9+19.9+199.9-0.4
1.9+19.9+199.9-0.4
=2-0.1+20-0.1+200-0.1-0.4
=2+20+200-0.1×3-0.4
=222-0.7
=221.3

上式可化为
2-0.1+20-0.1+200-0.1-0.4
= 222-0.7
= 221.3

221.3

2+20+200-0.4-0.1-0.1-0.1