Not only are Celsius and Fahrenheit degrees different sizes ... And to do it the other way around: 72 Fahrenheit is 40/2, which is 20 Celsius. You can even use 30 instead of 32, ...

Temperature conversion represents one of the most frequently encountered mathematical operations in academic science, yet traditional methods often prove cumbersome during time-pressured examinations.

C to F: Multiply the temperature by 2 and then add 30 (actual formula is multiply by 1.8, add 32) ex: 22 C is roughly equal to 74 degrees using my method, actual conversion is 71.6 ...