Mental Math for Pilots Practice Test

To convert Celsius to Fahrenheit you scale the temperature by 9/5 (which is 1.8) and then add 32 to account for the different zero points. The correct expression is Fahrenheit equals 9/5 times Celsius plus 32, or F = (9/5) × C + 32, often written as F = 1.8C + 32. The 32 is the Fahrenheit value at 0°C, so you first adjust the size of a degree, then shift the zero point.

If you add 32 before multiplying, you’d effectively apply the offset to the scaled value as well, leading to an incorrect result. Using 2 as the multiplier is not accurate because a 1°C change equals 1.8°F, not 2°F. The form that uses (Celsius − 32) × 5/9 is the inverse direction (it converts Fahrenheit to Celsius) and doesn’t give Fahrenheit from Celsius.