Rational number:
These numbers can be written as a simple fraction.
Example:
1/2, 3/5, 10/22 etc
Irrational numbers:
These numbers cannot be written as a simple fraction.
Example:
π = 3.14159 …
As you can see the decimal numbers are keep on repeating but they are different,
Another example of an irrational number is given below.
√2 = 1.414213 …
There is no way to represent this number as a simple fraction.
Now let's come to the given question.
9/16 is indeed a rational number since it is written as a simple fraction.
Also, the number 11/20 is a rational number since it is written as a simple fraction.