Logical Venn diagrams test how three classes are related: one inside another, overlapping, or completely separate. They also include reading numbers off a three-circle diagram. ASO has not asked this topic in 2012–2025, but OSSC and other exams do.
Relationships
- Inside: every member of A is also in B (Rose → Flower → Plant).
- Overlap: some members are common (Doctors and Women).
- Separate: nothing is common (Pen, Table, Bucket).
Take the classes two at a time, decide inside, overlap or separate for each pair, then pick the diagram that shows all three pairs correctly.
Number questions
- "Only A" = the part of A that touches nothing else.
- "A and B but not C" = the overlap of A and B outside C.
- "Exactly two" = add the three two-way overlaps; "exactly one" = add the three "only" parts.