"NO! That's like something out of Monty Python"

came the response from someone else.
I had commented on a post by a friend who was saying that the girl in the tea room had not been able to give her the right change. When told she had not done this the girl had to start all over again. She couldn't just add the extra 20p. 
Further into the conversation I made a comment about the way in which I had once bought ten hinges at a hardware store for the Senior Cat. They all cost the same amount. The boy who sold them to me would have been in his late teens I suppose. He stood there and solemnly wrote the number down ten times and then added it up. When I gently pointed out that all he had to do was add "O" to the first one he appeared to be completely confused. I gave up.
Pythonesque? I suppose so. 
I always go to the checkout in the supermarket with a fairly accurate idea of what the final total is going to be. It can be difficult if I buy something that needs to be weighed but I always have some idea of what I expect to pay. I check my receipts. It is a habit born of never having had a lot of money. 
I can stand in the supermarket and do a quick calculation about which is the better buy - and whether I can afford it. It is all basic arithmetic.
When I knit something I can work out the number of stitches needed for multiple repeats and the number of rows between decreases or increases. It is also basic arithmetic.
I would have to look up the proof for any geometrical theorem now because I haven't used one in years but I can still know about right angled triangles and the square on their hypotenuse. I can still divide squares, triangles and circles to make them do what I want them to do.  I know my fractions and percentages.
I am not a mathematician. I was taught maths very badly indeed. Statistics was not my favourite subject at university - but I can still do the basic statistical tests I need and I can read other people's work in my areas and the statistics they use. 
Most people don't need those skills in everyday life but they still need a basic understanding of everyday arithmetic. They need to be able to use money - and understand how much money they can  use.
I don't own a credit card. It's not that I don't think I could handle one but there are other ways of doing essential things and I know that I won't owe money. 
Ms W's understanding of basic arithmetic is good. Her father saw to that and I encouraged it. She can do mental calculations because he father refused to let her use a calculator. Her classmates are often a little more hesitant but her school has been very good about making sure that the girls have that training too. Ms W can do their weekly household shopping just as efficiently, perhaps more so, than her father.  It is something she has had to learn to do because she has no mother. 
And perhaps that's the real problem. Most people don't need to use even basic arithmetic in everyday life. If you pay for everything with a card then you don't even need to hand over money and get the change. 
No wonder people find themselves in debt.