89*99+99 怎嘛简便运算?

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89*99+99 怎嘛简便运算?

89*99+99 怎嘛简便运算?
89*99+99 怎嘛简便运算?

89*99+99 怎嘛简便运算?
89*99+99
=99*(89+1)
=99*90
=(100-1)*90
=100*90-90
=9000-90
=8910

=(90-1)*99+99
=90*99-99+99
=90*99
=90*(100-1)
=90*100-90
=9000-90
=8910

(89+1)*99=90*99=90*(100-1)=90*100-90=8910.