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Problem presentation. Meng Li. Problem Set 3. #22:In a survey of 100 undergraduate math majors at a certain university, the following information is obtained about the courses they are taking during the spring semester: 41 are enrolled in real analysis
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Problem presentation Meng Li
Problem Set 3 • #22:In a survey of 100 undergraduate math majors at a certain university, the following information is obtained about the courses they are taking during the spring semester: • 41 are enrolled in real analysis • 44 are enrolled in differential equations • 48 are enrolled in linear algebra • 11 are enrolled in both real analysis and linear algebra • 14 are enrolled in both real analysis and differential equations • 19 are enrolled in both differential equations and linear algebra • 10 are not enrolled in any of these three courses • How many students are enrolled in all three of these courses?
There are lots of information, what can we do? Venn diagram must be the best choice!
Solution: See Blackboard ^-^
Easy way to solve the problem: • The Principle of Inclusion-Exclusion: • If A1, A2, …, An are n≥2 finite sets, then: • |A1∪A2∪…∪An|=∑1≤i≤n|Ai|-∑1≤i<j≤n|Ai∩Aj|+∑1≤i<j<k≤n|Ai∩Aj∩Ak|-… +(-1)n+1|A1∩A2∩…∩An|