tl;dr: Yes, it is a rational number.
Hello!
A rational number is a number that can be expressed as a fraction.
Remember, rational numbers are also numbers that have a repeated pattern (ex. 1.33333333...)
So, since you're asking whether 0.111111111... is rational or not, your answer will be yes, 0.111111111... is a rational number.
Hope this was helpful. Have a great day!
