My favorite thing used to be putting me hand over the small screen on their POS (Point of Sale) and asking them to count back my change.Yes I see it all and I'm told by my one daughter who is a teacher's aid.
Like going to the store they just hand a hand full of change and say the amount.
Warren
Better yet is letting them punch in the amount and then adding change.
I spent about an hour today trying to explain simple algebra to my cousins. They are my age (60's) which is really really sad. I guess fruit doesn't fall far from the tree?