用简便方法计算:1999*199.8-1998*199.7,求求,
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![用简便方法计算:1999*199.8-1998*199.7,求求,](/uploads/image/z/600296-32-6.jpg?t=%E7%94%A8%E7%AE%80%E4%BE%BF%E6%96%B9%E6%B3%95%E8%AE%A1%E7%AE%97%EF%BC%9A1999%2A199.8-1998%2A199.7%2C%E6%B1%82%E6%B1%82%2C)
用简便方法计算:1999*199.8-1998*199.7,求求,
用简便方法计算:1999*199.8-1998*199.7,求求,
用简便方法计算:1999*199.8-1998*199.7,求求,
1999×199.8-1998×199.7
=(1998+1)×199.8-1998×(199.8-0.1)
=1998×199.8+199.8-1998×199.8+1998×0.1
=199.8+199.8
=399.6