The temperature in degrees Celsius (C) can be converted to degrees Fahrenheit (F) using the formula F(C)= 9/5 C+k, where k is a constant. Find k, if to C=−40ºC corresponds F=−40ºF.

Answer 1

F(C) = 9 / 5 C + k

− 40º F = 9 / 5 ∙ ( - 40°C ) + k

Mathematically:

− 40 = 9 / 5 ∙ ( - 40 ) + k

− 40 = 9 ∙ ( - 40 ) / 5 + k

− 40 = - 360 / 5 + k

− 40 = - 72 + k

Add 72 to both sides

− 40 + 72 = - 72 + k + 72

32 = k

k = 32