Opinion: Why do we think it's a huge joke if we're bad at maths? It could be a matter of life and death, says Sharon Griffiths.

Sometimes things just don't add up…

But if you're no good at maths, how would you know? And does it matter? Of course it does.

Among the minor goodies in last week's budget was £600 for schools per student studying A-level maths. It's the chancellor's way of getting us to take maths seriously.

Well, good luck with that…

Because we don't take maths seriously. If we're hopeless at adding up, put the decimal point in by guess work and haven't a clue what trigonometry is for, then it's all a bit of a joke. Well-educated people are happy to boast about how useless they are at maths, as if it doesn't matter at all, tra la. Even John Humphreys – who would go apoplectic at a misplaced apostrophe – can laugh sympathetically on Radio 4 about 'maths blindness.'

We don't laugh when people can't read. So why is it funny when they can't add up?

As a nation we're getting worse, plunging merrily down the international rankings. Doesn't bode well.

I just scraped through O-level maths and only once in my life have ever found a use for Pythagoras' theorem – to work out how much I further I swam if I went diagonally across the pool instead of up and down – but still use maths of some sort most days.

There is much fuss at the moment to teach personal finance in schools. An excellent notion. But maths is the basis of much of that. Anyone who doesn't immediately grasp the difference between 3% interest and 30% interest is a lamb to the financial slaughter.

I remember the misery, at ten years old, of having to work out compound interest. No calculators, of course, just endless workings-out that rambled over pages and pages of my exercise book.

But at the end I understood very well how it worked, how much 5% interest added to a total. It was a lifelong lesson and probably more useful than all those men filling baths. It's also why decades later I was the queen of interest free credit cards.

I wonder how many people in a dreadful mess of debt are there not because they didn't understand money, but because they just can't do the sums.

Yes of course we need people to understand advanced maths – we need engineers and scientists to build our world. Many of those people doing A-level maths will go on to do that.

But we all of us need a basic grasp of arithmetic so we have an instant and instinctive understanding of what figures mean.

Shadow Home Secretary Diane Abbott, who read History at Cambridge, is certainly not dim but when she was asked how she'd fund extra police that Labour promised, she floundered spectacularly as she didn't have a clue what the figures meant.

Embarrassing, yes – but not as bad as the occasions when young medics couldn't understand the difference a decimal point makes and have given injections ten or a hundred times the proper dose and people have died.

Still think being hopeless at maths is a joke?