How old do you think you look compared to your real age? Do you get carded every time you go to the bottle shop or have you been buying without showing ID for ages even though you're only sixteen? Can you get away with paying cheap fares because the bus drivers think you're a student? Or a teacher? What are the advantages and disadvantages?
I'm almost 19, most common guess is 14-16. Nobody takes a word I say seriously but I can totally do that cheap student fares thing.