"Celsius=5/9*(Fahrenheit-32)" and "Celsius=5*(Fahrenheit-32)/9 "

The reason for multiplying by 5 and dividing by 9 instead of just multiplying by 5/9 is that in C, as in many other
languages, integer division truncates: any fractional part is discarded. Since 5 and 9 are integers. 5/9 would be
truncated to zero and so all the Celsius temperatures would be reported as zero.