My little kid last time when I brought him in a mall had been amazed with that thing used by the cashier that can summed up the cost of all what you bought. I told him that it was just a barcode scanner. Although it is very common to us, for all kids it is always be an unfamiliar thing that can bring to open their curiosity. It’s good for us adult to hear our children their questions because of their ability to learn in something.