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Questions › DSE › DSE 2006 › Q54
2 marksMathematics › Real analysis › Topology of the real line: open, closed and compact setsHardabout 3 min

DSE 2006 Question 54: Real analysis

Consider a Society consisting of individuals who may belong to various sets called Families and/or Gangs, with the rules: the entire Society is a Family; the empty subset is a Family; the set of individuals belonging to every Family in any collection of Families is a Family (arbitrary intersections); the set of individuals belonging to either of two Families is a Family (finite unions); and a set is a Gang if and only if the set of individuals not in it constitutes a Family. The intersection of two Gangs is necessarily

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Real analysis has come up 38 times in 5 exams since 2005.

What this question tests

This question is on Topology of the real line: open, closed and compact sets, part of Real analysis in Mathematics.

Which sets are open, closed or compact and how unions and intersections behave.

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Question from the DSE 2006 paper. Solutions are TestStop's own. Not affiliated with or endorsed by any examination authority.