Intersection means both
A ∩ B contains elements shared by A and B. Put this overlap into a Venn diagram first.
CSEC Math LabLearn · practise · master
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11 min
Section 3Sets
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Represent sets, describe their relationships and use Venn diagrams in real-world problems.
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Learn the idea
Three things to notice
Union means at least one
A ∪ B contains everything in A or B, including the intersection only once.
The complement sits outside
A′ contains every element in the universal set that is not in A.
Do not memorise the words alone. The worked example shows how to choose and apply the idea.
Syllabus coverage
Set notationSubsetsUnion and intersectionComplementsTwo-set Venn diagramsThree-set problems