Why is negative 40 degrees Celsius equal to negative 40 degrees Fahrenheit?

It just happens that the conversion formula from Celsius to Fahrenheit (and vice versa) gives this result. Here is the conversion formula for -40 C to Fahrenheit:

• F = (C x 1.8) + 32
• F = (-40 x 1.8) + 32
• F = -72 + 32
• Fahrenheit = -40°