72×9.9 简便运算
问题描述：
72×9.9 简便运算
答
=72×(10-0.1)
=72×10-72×0.1
=720-0.72
=712.8
72×9.9 简便运算
=72×(10-0.1)
=72×10-72×0.1
=720-0.72
=712.8