GCSE Maths: Venn Diagrams and Set Notation Guide

Set notation

ξ represents the universal set (everything being considered). ∩ means intersection (in both sets). ∪ means union (in either set). A dash (A′) means the complement (everything not in set A).

Drawing a Venn diagram

A Venn diagram uses overlapping circles inside a rectangle (the universal set) to show how items are grouped, with the overlap showing items belonging to more than one set.

Using Venn diagrams for probability

Once a Venn diagram is filled in, probability questions become a case of counting how many items satisfy the condition and dividing by the total number of items.

Common mistakes

• Placing an item in both circles when it should only be in one, or vice versa.
• Misreading intersection (∩) and union (∪) symbols.
• Forgetting items outside both circles still count towards the universal set total.