6.9×9.9+31×0.99的简便方法

分类: 作业答案 • 2022-01-31 11:16:31

问题描述：

答

6.9×9.9+31×0.99
=6.9x10-6.9x0.1+31x1-31x0.01
=69-0.69+31-0.31
=69+31-0.69-0.31
=100-1
=99