Those numbers which can be in form p/q (q≠0)
for example 3/5,4/3
To check whether a no. is rational or not
it should terminating or repeating decimal
0.8 ,0.3333 etc..
π=3.1415926535897932384626433832795.. is irrational number
Now find whether
7/21 ,4/9 and 0.8789453.. are rational or not..