Which of the following numbers is irrational?

Irratonal numbers can't be written as a/b where a and b are integers and b≠0

so if it can be written in form a/b then it is not irrational

, it's rational

1/5 is rational

it's irrational because we can't simplify the square root further

6.3=6.3/1=63/100, rationanl

answer is is irrational