The non-wind side of the CRAP-1 is just a standard slide rule, which is a 200 year old multiply/divide tool. It is bent around into a circle; that's all, and has marks at aviation-relevant places e.g. litre/gallon conversions (3.8) etc.
If you google on 'slide rule' you will see how it is used for mult/div.
Once you suss how to use a slide rule to divide 355/9 and then (mentally) put the d.p. in the right place, you are done. This process is in no way aviation (or CRAP-1) related.
I could not go for 3hrs without a pee
