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Contests
National and Regional Contests
Germany Contests
QEDMO
2007 QEDMO 4th
11
11
Part of
2007 QEDMO 4th
Problems
(1)
set S_{k} contains infinitely many multiples of m
Source: 4th QEDMO 2007 p11
11/9/2020
Let
S
1
,
S_{1},
S
1
,
S
2
,
S_{2},
S
2
,
.
.
.
,
...,
...
,
S
n
S_{n}
S
n
be finitely many subsets of
N
\mathbb{N}
N
such that
S
1
∪
S
2
∪
.
.
.
∪
S
n
=
N
.
S_{1}\cup S_{2}\cup...\cup S_{n}=\mathbb{N}.
S
1
∪
S
2
∪
...
∪
S
n
=
N
.
Prove that there exists some
k
∈
{
1
,
2
,
.
.
.
,
n
}
k\in\left\{ 1,2,...,n\right\}
k
∈
{
1
,
2
,
...
,
n
}
such that for each positive integer
m
,
m,
m
,
the set
S
k
S_{k}
S
k
contains infinitely many multiples of
m
.
m.
m
.
Sets
number theory
multiple