Which number is an irrational number

Answer:
The only irrational number if √9/31
Step-by-step explanation:
Rational numbers can all be written in the form of a/b in which both a and b are integers. 9/31 is already written that way. When we take the square of the first one, we get 3/4. And 0.66666 is 2/3. Therefore, only √9/31 is not a rational number.