A formula tells you how to work out something given another piece of information.

The formula F = 1.8C + 32 is used to convert a temperature in Centigrade to one in Fahrenheit.

When C = 10, we substitute this value into the formula to get:

F = 1.8 x 10 + 32

F = 18 + 32

F = 50

This means that 10º C is the same as 50º F