简便计算3.9×9.9

分类: 作业答案 • 2022-06-07 16:50:02

问题描述：

简便计算3.9×9.9

答

3.9×9.9
=3.9×(10-0.1)
=3.9×10-3.9×0.1
=39-0.39
=38.61

答

=(10-0.1)×3.9
=10×3.9-0.1×3.9
=39-0.39
=38.61

答

3.9×9.9
= 3.9 × （10 - 0.1）
= 39 - 0.39
= 38.61