Define x % a as the remainder obtained when x is divided by a.
Let f:Z→R be defined as f(x)=x % k, where k ϵ N. If Y is the range of f(x), then
n(Y)=k
Given x is an integer and k is a natural number, x can be expressed as
x=q.k+r, where q,r ϵ Z and 0≤r<k.
i.e. the remainder can be any value from 0 to k-1
⇒r ϵ {0,1,2.......k−1}⇒f(x) ϵ {0,1,2........k−1}⇒Y={0,1,2,..........k−1}⇒n(Y)=k