Four degrees Celsius is 40 Fahrenheit, and 40 Celsius is 104 Fahrenheit. So if you're on vacation and you hear it’s going to be 32 today, you know that that’s more than 28 (82 Fahrenheit) but ...

Multiply the temperature, 27, by 1.8. 27x1.8 roughly equals 49. Then add 32 to 49. That will give you 81 degrees Fahrenheit.