Is 2.55 a irrational, rational, integer, whole number or natural number?

So, the first thing we need to know is what is what.

So, A natural number is a whole number

A whole number is an integer

and An integer is a rational number.

Now, since there is a terminating decimal (a decimal that does not go on forever) we know it is a rational number.

Since there is a decimal, it cannot be an integer, therefore

It is a rational number