These are problem sheets I made for my school maths society, aimed at sixth-formers (i.e. students in their last two years of school.)
The problems are taken from a variety of sources, including V. V. Prasolov’s Problems in Plane Geometry and various UKMT Handbooks.

2016-2017

Induction
Geometry 1: Triangles
Geometry 2: Circles
Graph Theory
Geometry 3: Similarity
Geometry 4: Inversion
Geometry 5: Inversion 2 - Harder Problems
Geometry 6: Plane Isometries

2017-2018

Modular Arithmetic
Catalan Numbers
The Pigeohole Principle
Combinatorial Invariants
Logic Puzzles
Conic Sections
Inequalities 1
Inequalities 2: The Rearrangement Inequality
Helly’s Theorem