In: Advanced Math
Show that for any k ≥ 2, if n + 1 distinct integers are chosen from the set [kn] = {1, 2, . . . , kn}, then there will be two integers which differ by at most k − 1. Please demonstrate the steps so that I can learn from it and solve other problems by following the reasoning!
We first suppose that the given result is not true and will later see that this assumption leads us to a contradiction.
So, suppose we can choose n+1 distinct integers from the set
[kn] = {1,2, . . . , kn} such that the difference between any two
of them is at least k, Where .
Let these chosen integers are arranged in a increasing order and
denote them as
So,
[ Since the difference between
and
is at least
k]
This is a contradiction because cannot be larger than
the largest element kn of the set [kn].
Hence our assumption leads us to a contradiction. So our
assumption was wrong. Hence, for any , if n+1
distinct integers are chosen from the set [kn] = {1,2, . . . , kn}
, then there will be two integers which differ by at most k-1.
(Proved)