Sets summary

Key learning points

• Union $\cup$ = either set; intersection $\cap$ = both.
• Complement $A'$ = not in A (within the universal set).
• Shading and two-way counting problems are common exam tasks.

Worked example 1 — Intersection

$A=\{1,2,3\}$, $B=\{2,3,4\}$. $A\cap B$?

Working

In both sets.

Worked example 2 — Union

$A\cup B$?

Working

In either set.

Worked example 3 — Complement

$\mathcal{E}=\{1..5\}$, $A=\{1,2\}$. $A'$?

Working

Not in $A$.

Scaffolded Learning Sheet and answers (PDFs)

This page is a short, searchable overview for revision and search engines. Use the Scaffolded Learning Sheet first, then the Answers PDF for a full written solution. The printable PDFs remain the main classroom resource.