The formula for converting degrees Celsius to degrees Fahrenheit is

F = 9/5 C + 32

So it is customary to multiply the Celsius value by 9 and divide it by 5 before adding 32 to the result. A little manipulation of the formula will make it suitable to mental calculation. The decimal equivalent of 9/5 is 1.8 which is simply 2 – 0.2. So a more user friendly form of the conversion is

F = 9/5 C + 32 = 1.8 C + 32 = **(2 – 0.2)C + 32**

This short cut can be better understood if we take simple examples:

Example 1: 45^{o}C = 113^{o}F

a) Double the Celsius value **45 **to get 2C: **45 x 2 = 90**;

b) Move the decimal point of 2C one place to the left to get 0.2C: **90 x 0.1=9.0**

c) Subtract 0.2C from 2C : **90 – 9 = 81**

d) Add 32 to the result :**81 + 32 = 113**

Example 2: **37 ^{o}C**

**a) ****2C** = **2 x 37 = 74**

**b) ****0.2 C = 74 x 0.1 = 7.4**

**c) ****2C – 0.2C = 74 – 7.4 = 66.6**

**(2C- 0.2C) + 32 = 98.6 ^{o}F**

Celsius to Fahrenheit conversion, made easy, with a MATH-Inic short cut!