请教小学数学:用简便方法计算18.9*178.178+0.49一17.8*189.189
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请教小学数学:用简便方法计算18.9*178.178+0.49一17.8*189.189
![请教小学数学:用简便方法计算18.9*178.178+0.49一17.8*189.189](/uploads/image/z/428816-56-6.jpg?t=%E8%AF%B7%E6%95%99%E5%B0%8F%E5%AD%A6%E6%95%B0%E5%AD%A6%3A%E7%94%A8%E7%AE%80%E4%BE%BF%E6%96%B9%E6%B3%95%E8%AE%A1%E7%AE%9718.9%2A178.178%2B0.49%E4%B8%8017.8%2A189.189)
18.9*178.178+0.49一17.8*189.189
=189*17.8178+0.49一17.8*189.189
=189*(17.8+0.0178)+0.49一17.8*(189+0.189)
=189*17.8+189*0.0178+0.49一17.8*189—17.8*0.189
=189*0.0178+0.49—17.8*0.189
=0.189*17.8+0.49—17.8*0.189
=0.49
=189*17.8178+0.49一17.8*189.189
=189*(17.8+0.0178)+0.49一17.8*(189+0.189)
=189*17.8+189*0.0178+0.49一17.8*189—17.8*0.189
=189*0.0178+0.49—17.8*0.189
=0.189*17.8+0.49—17.8*0.189
=0.49