简便算法 1.78乘七十九分之七十八 2.2006乘两千零五分之两千零四

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78×（78/79）
=(79－1)×78/79
=79×78/79－1×78/79
=78－78/79
=77又1/79

2006×2004/2005
=(2005＋培高1)×2004/2005
=2005×2004/2005＋1×2004/雀芹2005
=2004＋顷中毕2004/2005
=2004又2004/2005

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