读了《中小学数学》(上旬)2015年第1、2期上刊登的刘坎乐的《教学一得》,颇有收获。笔者为刘老师严谨的作风和广博的知识所折服,但反复品读该文,觉得刘老师的解题指导尚有不妥之处,写出来与各位专家、同行一起探讨。题目;移动公司有两种优惠用户的计划,如下表。当用户的每月通话时间最少是多少分钟时,两种计划的话费是相等的?学生解答该题时先后有两种不同的方法和结果。一种是:60-40=20(元),20÷0.2=100(分钟),100+60=160(分钟)。通过验算结果是正确的。另 Read the “primary and secondary mathematics” (early) 2015 first and second issue of Liu Kan Le’s “teaching a get” quite successful. I was impressed by the rigorous style and extensive knowledge of Teacher Liu, but repeated reading of the article, I think there is a problem with Liu’s solution guidance, written together with experts and colleagues to explore. Topic; mobile company has two kinds of discount user’s plan, the following table. When the user’s monthly talk time is at least minutes, the two plan calls are equal. Students answer the question has two different methods and results. One is: 60-40 = 20 (dollars), 20 ÷ 0.2 = 100 (minutes), 100 + 60 = 160 (minutes). The result of checking is correct. another