CDS Mathematics · Teaching notes

Sets — CDS Elementary Mathematics

Sets has 28 past-year questions in CDS Elementary Mathematics, in 11 of the twenty-one sittings from 2016 (II) to 2026 (II). Twenty of them are Venn-diagram counting, most in sets of three or four on one paragraph; the other eight test what a set is. The first page covers set operations and special sets, the second counting with two and three groups.

Every subtopic, worked example, formula and trap in one printable document — answers shown, ready to share.

All 28 past questions CDS Mathematics strategy CDS home

Subtopic notes

Formula & revision sheet

3 formulas · 4 gotchas across all subtopics — the exam-eve cheat-sheet

Sets and Set Operations

Formulas (1)

Members, operations and special sets · Difference $A - B = \{x : x \in A,\ x \notin B\}$

Watch out for (2)

{0} is not empty
→ Members, operations and special sets
Large is not infinite
→ Members, operations and special sets

Venn Diagrams and Counting

Formulas (2)

Two groups · Two sets $|A \cup B| = |A| + |B| - |A \cap B|$
Three groups · Three sets $|A \cup B \cup C| = \textstyle\sum|A| - \sum|A \cap B| + |A \cap B \cap C|$

Watch out for (2)

Passed in both is not 100 minus failed in both
→ Two groups
Pairwise figures include the centre
→ Three groups

PYQ weightage by concept

3 concepts · 28 PYQs — where the marks actually sit, so you know what to drill first

Sets and Set Operations8 PYQs · 29%

Concept	PYQs	Share
Members, operations and special sets	8	29%

Venn Diagrams and Counting20 PYQs · 71%

Concept	PYQs	Share
Three groups	13	46%
Two groups	7	25%

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Sets and Set Operations

Venn Diagrams and Counting

Formula & revision sheet

PYQ weightage by concept

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