Whitstable Maths: Mental Arithmetic
A friend of mine bought some goods from a well known local supermarket. The bill came to £4.96. He handed the assistant a fiver and then, to minimise the change in his pocket, another 6p.
That’s clear enough isn’t it? He was expecting 10p in change, instead of which the shop assistant gave him £1. So, being an honest sort of a chap, he told the girl that she’d made a mistake.
“What, haven’t I given you enough?” the assistant groaned, obviously peeved at the complex mental manoeuvres she was being asked to perform.
“No, you’ve given me too much,” he said, and then patiently began to explain what it was he was expecting. Even then she couldn’t get it right and gave him 20p instead. At which point my friend gave up. “You just can’t help some people,” he thought, pocketing the money.
Those of us brought up on mental arithmetic would have had no problem with this. We learned to add and subtract in our heads. When I was a barman, before the advent of electronic tills, you would have to tot the bill up as you were going along. Woe betide you if you made a mistake, as the customer was usually keeping a tally too, and would be quick to point it out to you.
What are the kids being taught these days? At one stage they were allowed to use calculators in their maths exams. I don’t know if this is still the case, but one thing is certain: they can’t add up any more.
With tills that do it all for you, there’s no incentive for people to learn the simple art of mental arithmetic. It’s a matter of training. If you never walked your legs would shrivel up. It’s the same with the brain. You need to put it to work in order for it to function properly.
No one is asking shop assistants to engage in trans-dimensional calculus while they’re adding up your bill, but they should at least be able to tell the difference between a 10p piece and a £1 coin.
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