One of my little neighbours is 11 years old, and she was watching me applying replacement house numbers to my wall this evening.
'Oh, I wonder if I have put this zero the right way up,' said I, expecting to mislead her, but the detail of her instant reply surprised me:
'It doesn't matter Andrew because it has rotational symmetry... Now you see that is an example of a practical application of mathematics.'
Clearly I will need to keep my wits about me as our frequent conversations progress.
I did, however, feel it necessary to point out that as it was an oblong zero rather than a perfect circle, it only had symmetry through a 180 degree rotation, as opposed to any degree of rotation.
'So what you mean is it doesn't matter what way up you put it, like I was trying to tell you,' she told me, with a tone of indulgent patience that would be more appropriate from adult to child than from child to adult.