Cambridge O Level Mathematics (Syllabus D) · Syllabus 4024 · Number
Sets
What is Sets?
A set is a well-defined collection of distinct objects called its elements, described either by listing the elements inside braces or by a rule in set-builder notation. Set language provides the operations union, intersection and complement, all taken relative to a stated universal set, and a Venn diagram is the standard picture used to count the elements of each region.
This definition is part of the Number chapter in Cambridge O Level Mathematics (Syllabus D).
Sets in context
A Venn diagram is a counting device, not a picture. The reliable method is always the same: fill the most-overlapped region first and work outwards, because every other region is then a subtraction from a number you already know. For two sets that means the intersection, then the “only” regions, then the outside; for three sets it means the triple overlap, then the three pair-only regions, then the three single-only regions, then the outside.