Question

any number when divided by same number became unity why
.

Answer 1

if you divide any no. by itself it will become 1
one is a unit no. (contains only one digit)

Answer 2

division means dividing a particular given data in a few given units(easy language)..
for example if u distribute 10 chocolates in 5 students, everyone will get 2 chocolates. so we've
10/5=2
similarly a number divided by itself is like distributing x no. of chocolates in x students.
so we've
x/x=1(unity)
Hence Proved.