Rational number is the number that can be made into ratio. In this case,
0.02= 1/50
2= 2/1
sqrt 2= irrational
sqrt 1/2= irrational
In general, the number in sqrt mostly irrational with an exception on the number that can be solved t remove the sqrt. The example would be √4 which can become 2 or √1/4 which can become 1/2