Hi Doris. Celsius and Fahrenheit are just two scales that measure the
same thing: temperature. There are two differences:
a) the size of the units. 1 degree Fahrenheit is 5/9 of a degree Celsius.
b) where Zero is. 0 degrees celsius is 32 degrees Fahrenheit.
Now to convert between them, we just use these two.
(Temperature in Fahrenheit  32 ) (5/9) = temperature in Celsius.
for example
212 degrees Fahrenheit is ( 212  32 ) (5/9) = 100 degrees Celsius.
(Temperature in Celsius) (9/5) + 32 = temperature inFahrenheit.
for example
0 degrees Celsius is 0 (9/5) + 32 = 32 degrees Fahrenheit.
In fact, the celsius scale was chosen because it makes things simple:
the freezing point of water is 0 and the boiling point is 100. Easier
numbers to remember than 32 and 212 in my opinion!
PS: Here in Saskatchewan, Canada, our winter temperature sometimes
reaches 40 degrees! At that temperature, whether you use Fahrenheit
or Celsius doesn't matter. Can you see why? :)
Stephen and Penny
