pigeonhole principle questions centered
122294
How to rotate $2n$-sliced pizza so half the people are happy
75852
Using Pigeonhole Principle to prove two numbers in a subset of $[2n]$ divide each other
101179
Partition of a set and Hall's theorem
98744
How to distinguish between permutation and combination questions?
72591
Find a bijection to prove a fact about integer partitions
18429
Counting measure proof
47161
Quick logic question about $P\leftrightarrow Q$, terminology
17544
another topology multiple choice
66948
Proving question on sets
77286
Proving set theory question
94923
Using the Pigeonhole Principle to show that $2$ of any $n+1$ numbers from $\{1,2,\ldots,2n\}$ sum to $2n+1$
52572
Questions relating to inclusion-exclusion principle
53312
Multiplication principle and permutation
101734
$7$ points inside a circle at equal distances
104309
Pigeon-Hole Principle Common Sum
37448
Two Circles and Tangents from Their Centers Problem
73287
Project Euler Question 14 (Collatz Problem)