How old would you be if you didn't know how old you are?

This phrase keeps popping up. I had it posted on my office door three weeks ago. Two weeks ago my brother quoted it at a picnic. And just now I found Cold Marble pointing to it here.

Answer for me: most days, in my early 40's. When I'm playing with the nieces and nephews, about 15. When I've sat too long, 85. How old would YOU be if you didn't know how old you are?