85×199×85怎样简便计算
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85×199×85怎样简便计算
85×199×85怎样简便计算
85×199×85怎样简便计算
85×199×85
=85×85×199
=7225×(200-1)
=7225×200-7225
=1445000-7225
=1437775
其中85×85=7225是有一个口诀的,积的前面两位等于8×(8+1)=72,后面是25
85x199x85
=(100-15)²x(200-1)
=(100²-2x100x15+15²)x(200-1)
=(10000-3000+225)x(200-1)
=7225x(200-1)
=7225×200-7225
=1445000-7225
=1 437 775
你这个题目应该是
85×199+85 吧85×199+85
=85X(199+1)
=85X200
=17000
85X199X85=(80+5)^2x(200--1)
=(6400+800+25)x(200--1)
=1280000+160000+5000--7225
=1445000--7225
=1437775.