Dividing a Set into Subsets & The Pigeonhole Principle
53937
Any partition of $\{1,2,\ldots,100\}$ into seven subsets yields a subset with numbers $a,b,c,d$ such that $a+b=c+d$.
130771
Sets and the principle of inclusion and exclusion
5840
divides, not divides and cardinalities
158671
Cardinality of a set that consists of all existing cardinalities
10472
Is every set a subset?
42744
Prove a number is even using the Pigeonhole Principle
140044
A set union find algorithm
5215
Can the principle of inclusion/exclusion be used to count elements in the intersection of a sequence of sets?
94923
Using the Pigeonhole Principle to show that $2$ of any $n+1$ numbers from $\{1,2,\ldots,2n\}$ sum to $2n+1$
60309
Let X be a subset of {1,2,...,2014}...
106397
Counting ways to partition a set into fixed number of subsets
20973
How can I find all the subsets of a set, with exactly n elements?
147484
For a set with N members, what is the number of set partitions in which each subset is either of size 1 or 2?
146664
The union of two linearly independent subsets
82628
Cardinality of a set of closed intervals
83518
Proving Two sets have same cardinality
146098
Number of nonempty subsets of a set with $n$ elements