Mental Math for Pilots Practice Test

Converting Celsius to Fahrenheit uses the formula F = C × 9/5 + 32. For 20°C, multiply by 9/5 (which is 1.8): 20 × 1.8 = 36. Then add 32 to account for the freezing point: 36 + 32 = 68. So 20°C equals 68°F. A quick way to remember: 0°C is 32°F, and each additional degree Celsius adds 1.8°F, so 20°C adds 36°F to 32°F, totaling 68°F. In aviation contexts this kind of conversion is handy when charts or performance tables use Fahrenheit. The other options would correspond to temperatures around 18.9°C, 21.1°C, and 22.2°C, respectively, which are not equal to 20°C.