数学题(不来会后悔的!)1990*198.9-1989*198.8=?对了有分奖哦!
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![数学题(不来会后悔的!)1990*198.9-1989*198.8=?对了有分奖哦!](/uploads/image/z/12601471-31-1.jpg?t=%E6%95%B0%E5%AD%A6%E9%A2%98%EF%BC%88%E4%B8%8D%E6%9D%A5%E4%BC%9A%E5%90%8E%E6%82%94%E7%9A%84%21%EF%BC%891990%2A198.9-1989%2A198.8%3D%3F%E5%AF%B9%E4%BA%86%E6%9C%89%E5%88%86%E5%A5%96%E5%93%A6%21)
数学题(不来会后悔的!)1990*198.9-1989*198.8=?对了有分奖哦!
数学题(不来会后悔的!)
1990*198.9-1989*198.8=?对了有分奖哦!
数学题(不来会后悔的!)1990*198.9-1989*198.8=?对了有分奖哦!
(1989+1)198.9-1989*198.8
=1989*198.9+198.9-1989*198.8
=1989(198.9-198.8)+198.8
=198.9+198.8
=397.7
简便方法
原式=(1990-1989)*198.8+1990*(198.9-198.8)
=198.8+1990*0.1=198.8+199
=397.8
395811-395413.2=397.8
1990*198.9-198.9*1988=2*198.9=397.8
1990*198.9-1989*198.8
=(1989+1)*198.9-1989*198.8
=1989*198.9-1989*198.8+198.9
=1989*(198.9-198.8)+198.9
=1989*0.1+198.9
=198.9+198.9
=397.8
1990*198.9-1989*198.8
=1990*198.9-(1990-1)*(198.9-0.1)
=199+198.9-0.1
=397.8
1990*198.9-1989*198.8=199*10*198.9-1989*198.8=199*1989-1989*198.8=1989*(199-198.8)=199*0.2=(200-1)*0.2=200*0.2-0.2=39.8