Question

How do you convert Celsius to Fahrenheit in your head?

Answer 1

So if x is 20°C, the temperature in Fahrenheit is 1.8*20 + 32 = 68°F. To do it in your head, double the Celsius temperature, reduce the resulting figure by 10% then add 32. So 20°C → 40, minus 10% → 40 - 4 = 36. Add 32 → 68°F.