Sometimes the kids grumble over schoolwork and ask me whether I’ve ever needed to know the year when Gustav Vasa became king of Sweden, or some such thing. I must admit I haven’t.

Most of what I learned in school I’ve forgotten, except languages and some maths. Many parts of maths would probably come back if I ever made an attempt to refresh my memories, because it was more about doing than about memorizing. But all the fact-based subjects, from biology through physics to history, are mostly gone. The basic frameworks are there still, but none of the details.

Languages have been truly useful. English, of course, and French, and even the smattering of German I learned in university.

In a strong second place after languages comes basic geometry. Pythagoras’ theorem is good for all kinds of everyday problems, from shaping the sleeve of a knit cardigan to estimating the length of steel flowerbed edging. And the relationship between the radius and the area of a circle comes in surprisingly handy for estimating the size of a pancake pan, and hence the right amount of batter. If the radius of the large pan is about 50% larger than that of the small pan, then the amount of batter will be 100% larger. 0.5 dl for the small pan, 0.7 for the medium, 1 whole dl for the largest one. I could of course reach the same result with trial and error, but that’s less fun.