Is 1/8 rational or irrational?

A number is rational if it can be written as the ratio of two integers.
The ratio of two integers is a fraction, and you just did it.  Your number
is the ratio of 1 to 8 .  It's about as rational as you can get.

Here's a fun fact that's easy to remember:
ANY number that you can write down on paper, completely, with digits
and a decimal point or a fraction bar if you need them, is rational.

40%=2/550=1/230=3/1056=14/25