I think you are all being very unfair to the supermarkets. Far from trying to con us, they like many are aware of the growing problem of dementia and they are doing their best to help us keep older people keep their marbles for as long as possible by setting challenging mental arithmetic problems for us as we wander round the store.
When you reach 100 years old, open The Telegram and sup your glass of champagne, sound in mind, if not in body lift your glass and drink a toast to Tesco and Sainsbury's, who have set you all those challenging problems that have kept your mind fit and lively. 