Proof for : How many numbers cannot be expressed as a sum of two numbers which are chosen from a given set.
132041
Numbers which cannot be formed
119084
How many ordered pairs $(A,B)$ they are if $A$ and $B$ are subsets of $\{ 1,2,3,4,5 \}$ such that $A \cap B = \{1\}$?
65978
How many subsets does the set $\{1, 2, \dots , n\}$ have that contain no two consecutive integers if $1$ and $n$ also count as consecutive?
22154
Show that given a set of positive n integers, there exists a non-empty subset whose sum is divisible by n
23097
Prove that every number ending in a $3$ has a multiple which consists only of ones.
47123
Suppose that a set has an odd number of elements. Explain why half of the subsets will have an odd number of elements
7785
Cardinality of sum-set
24954
Prove that there are infinitely many integers of the form $111\ldots111$ that are multiple of $n$.
92772
How many different sets of $6$ different numbers can we construct from $11, 13, 18, 19, 19, 20, 23, 25$?
108941
Combinatorics Question Asking How Many Integer Solutions Given Different Restrictions
568
Consider a set $A$ of $10$ integers, $A = \{a_1,a_2, \ldots ,a_{10}\}$. Prove that there is at least one subset of $A$ whose sum is divisible by $10$.
37783
Proving that a set of 2016 natural numbers contain a non-empty set with a sum divisible by 2016
22391
Is the set of all pairs of real numbers uncountable?
4559
How many ways can $133$ be written as sum of only $1s$ and $2s$
103347
combinatorial proof of summation
156242
As many even numbers as natural numbers.
48523
Let $A$ be any uncountable set, and let $B$ be a countable subset of $A$. Prove that the cardinality of $A = A - B $