It's common in Vietnam to be asked your age, even by people you don't know very well. In the little restaurant I've been going to on Lư Quốc Sư, the woman who owns the place has been kind enough to tolerate my halting Vietnamese & I have achieved the status of a regular customer. So the other evening, as she was cleaning up my table, she asked, "Ông bao nhiêu tuổi?" and when I replied "Sáu mười một" (sixty-one), she replied, "Khỏe!" which means "healthy," but in this context meant something more like, "Wow! Not bad for an old guy!"