6.9×9.9+31×0.99的简便方法_数学解答

6.9×9.9+31×0.99的简便方法

人气：134 ℃　时间：2020-06-17 20:17:14

解答

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