THERMOMETRY.
In the Fahrenheit scale there are 180 degrees between the melting-point of ice and the boiling-point of water. In the Centigrade scale there are 100 degrees between the freezing and boiling point of water.
RULES FOR CONVERTING ONE
SCALE INTO THE OTHER.
To convert Fahrenheit degrees into those of Centigrade: Subtract 32, multiply by 5, and divide by 9. For example:
104° F. - 32° = 72; 72 × ⁵/₉ = 40° C.
To reduce Centigrade degrees into those of Fahrenheit: Multiply by 9, divide by 5, and add 32. For instance:
40° C. × ⁹/₅ = 72 + 32 = 104° F.