用简便方法计算4.05×2.9+0.405×70+0.405,急用.

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用简便方法计算4.05×2.9+0.405×70+0.405,急用.
用简便方法计算4.05×2.9+0.405×70+0.405,急用.

用简便方法计算4.05×2.9+0.405×70+0.405,急用.
4.05×2.9+0.405×70+0.405 =0.405×29+0.405×(70+1) =0.405×29+0.405×71 =0.405×(29+71) =0.405×100 =40.5