你好!正确解答过程如下。
90×31-91
=90×(30+1)-90-1
=90×30+90×1-90-1
=2700+90-90-1
=2700-1
=2699
如图所示
=90×(30+1)-90-1
更好!!
简便计算过程方法如下
解:90x31-91
=91x(31-1)
=91x30
=2730
90×31-91
=90×(30+1)-91
=2700+90-91
=2700+(90-91)
=2700-1
=2699
90x31-91
=91x(31-1)
=91x30
=2730