Answer:
It is a terminating decimal
Explanation:
You want to know how 104.25 is a rational number.
Rational number
A rational number is one that can be expressed as the ratio of two integers. Any terminating decimal can be expressed as such a ratio by considering the place value of the least-significant digit.
Here, the least-significant digit has a place value multiplier of 1/100, so the ratio of integers that has this value is ...

Besides terminating decimals, rational numbers also include repeating decimals. The length of the repeat is irrelevant, as long as there is one.
Some repeating decimals are ...

The reciprocals of many prime numbers have repeating decimals with as many digits as the prime, less 1. As you can see, 1/7 has 6 repeating digits; 1/19 has 18 repeating digits.
Any terminating or repeating decimal is a rational number. 104.25 is a terminating decimal.