Is 3.625 rational or irrational

3.625 is RATIONAL, because you have not indicated if it continues to infinity.

To continue to infinity then the number is written as 3.625... (Note the dots).

However, 3.625... is also rational , because it can be converted to a quotient(fraction).

NB Irrational Numbers have their decimal going to infinity AND the decimal digits are not in any regular order.

pi = 3.141592.... Is the most well known irrational number.

Other irrationsal numbers are the square roots of prime numbers.