小学三年级的某节数学课,因为有校领导旁听,已预先演练过多次的数学老师全神贯注,讲得格外认真。幕布上放映着幻灯片,画面上分别有一块铁和一堆棉花。数学老师和蔼地问:“哪位同学来说一下,一吨铁和一吨棉花哪个重?”同学们纷纷举了手,老师叫了我,我站起来回答道:“在日常环境中的一吨铁和一吨棉花,实际上棉花更重,二者在真空中才能称得准。”数学老师有些惊讶,不是因 A math class in the third grade of primary school, because of the leaders of the school, has been preoccupied with math teachers who have pre-drilled many times and spoke earnestly. A slide shows on the screen, with a piece of iron and a pile of cotton on the screen. Math teacher kindly asked: “Which students for a ton of iron and a ton of cotton?” The students have raised his hand, the teacher called me, I stood up and replied: “In the daily environment In a ton of iron and a ton of cotton, in fact, heavier cotton, both in the vacuum can be called accurate. ”Some math teacher surprised, not because