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在最近的教学检查时,我偶然发现学生作业中的误批情况。 [题]:锚标浮筒是打捞作业中用来标记锚或沉船位置的。它的上、下两部分是圆锥,中间是一个圆柱(如图)。按图中标出的尺寸,计算它的表面积(单位mm,精确到100mm2)。 (人教版义务教材《几何》第三册p.200第7题). 学生解出了“S=…=1040000π≈1040000×3=3 120 000(mm2)”,老师用红笔将之批改为“S=…=1040 000π≈1040 000×3.14=3 265 600(mm2)”,并在旁边批注“请注意精确度!”
During the recent teaching inspection, I stumbled upon the misappropriation in student work. [Question]: The anchor pontoon is used to mark the position of the anchor or sunken ship in the salvage operation. Its upper and lower parts are cones, and the center is a column (pictured). Calculate its surface area (in mm, accurate to 100 mm2) according to the dimensions indicated in the figure. (Personal Education Edition voluntary textbook “Geometry” Volume III p.200 Question 7). The student solved “S=...=1040000π≈1040000×3=3 120 000 (mm2)”, and the teacher revised it with a red pen. For “S=...=1040 000π≈1040 000 x 3.14=3 265 600 (mm2)”, and endorsed “Please note the accuracy!”