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众所周知,在解答有关包含与排除问题时,我们常常会用韦恩图来帮着分析思考。但如果单凭韦恩图这把利器,有时难免也会身陷黔驴技穷的窘境。最近,在辅导四年级奥数时我就遇到了这样一道三量重叠问题。原题是这样的:某班有40名同学参加课外兴趣小组,参加数学小组的有29人,参加语文小组的有21人,参加美术小组的有25人,有17人既参加了数学小组又参加了美术小组,有15人既参加了数学小组又参
It is well-known that we often use Wayne diagrams to help analyze and interpret answers to questions about inclusion and exclusion. But if Wayne diagram alone this weapon, and sometimes inevitably also be stuck in the dilemma. Recently, I encountered such a three-fold overlap when teaching fourth-year Olympians. The original title is this: a class of 40 students to participate in extra-curricular interest groups, mathematics group to participate in 29 people, to participate in the language group of 21 people, to participate in the art group of 25 people, 17 people both participated in the mathematics group Participated in the art group, 15 people participated in both the mathematics group and reference