66乘21加19乘21加85乘19用简便算法怎么算

分类: 作业答案 • 2023-01-08 20:20:10

问题描述：

答

66x21+19x21+85x19
=(66+19)x21+85x19
=85x21+85x19
=85x(21+19)
=85x40
=(90-5)x40
=90x40-5x40
=3600-200
=3400