Answer: Irrational
We cannot write
as a ratio of integers, so that's why it's irrational.
Note that
The decimal digits go on forever without any pattern. If the digits repeated themselves, then we would have a rational number.
A quick way to tell if it is rational or not, without using a calculator, is to note that 103 is not a perfect square. The list of perfect squares are:
1,4,9,16,25,36,49,64,81,100,121,...
we see that 100 is the closest perfect square, but 103 is not in that list. Each perfect square is of the form x^2, where x is some positive whole number.