Later On

A blog written for those whose interests more or less match mine.

Easy Celsius to Farhrenheit conversion you can do in your head

with one comment

Double the Celsius number, subtract 10%, then add 32. Result is the Fahrenheit number.

Example: 17ºC: twice 17 is 34; subtract 3.4 to get 30.6; add 32 to get 62.6: 62.6ºF, which is correct.

The reason it works is that it’s simply a restatement of the conversion formula F = 9/5 C + 32

You double the number and then subtract 10% of the doubled number, which amounts to 2x – (.1*2x).

Since .1*2 = .2, that’s the same as 2x – .2x. That’s the same as (2 – .2)x, which is 1.8

1.8 is the decimal representation of 9/5, so you can see that the mental conversion uses the exact conversion formula. The result is not an approximation, but the actual conversion.


Written by LeisureGuy

18 December 2016 at 2:31 pm

Posted in Daily life

One Response

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  1. Love this.

    Dave Anthony

    18 December 2016 at 2:38 pm

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