This is for my dear friends who will soon be travelling to Spain:
When I was in elementary school, we were taught, drilled and tested on the formulas for converting temperature measurements between Fahrenheit and Celsius. Celsius was known as Centigrade back then, but they both begin with C so it doesn't matter. :)
F = 9/5 x C + 32
C = 5/9 x (F - 32)
It was an all but useless exercise. How often do most people need to do those conversions? In the science lab, we use Celsius; otherwise, Fahrenheit. Except at our house, when I was young. The thermometer that my father bought and installed outside our window read only in Celsius, so I was kept busy converting it into the more familiar numbers. Even so, I never really learned the conversion formulas; I never could remember which way they went. How liberating it was, many years later, when I realized that I could easily figure that out, knowing 0C = 32F (water freezes) and 100C = 212F (water boils).
It wasn't until I was more than 30 years outside of elementary school, vacationing in New Zealand, that I discovered even greater freedom. All temperatures there are in Celsius (as they are in most of the world), and those old formulas were just too clumsy. So I amused myself by developing a much handier formula that was just fine for my purposes. (More)
