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    Re: The "golden rule of three" - what's that?
    From: Bill Lionheart
    Date: 2018 Feb 12, 08:51 +0000
    So now it is explained I realise I was taught this pre algebra approach to ratio problems aged 10 in 1972 in England. We were expected to understand the idea of proportion though rather than rote learning. But as navigators understanding is often the first to go with cold, tiredness and seasickness so then rote rules rule!

    Bill Lionheart

    On 12 Feb 2018 12:37 am, "Brad Morris" <NoReply_Morris@fer3.com> wrote:
    Tony

    It's just proportions 

    A/B = C/D

    Brad

    On Feb 11, 2018 6:27 PM, "Tony Oz" <NoReply_TonyOz@fer3.com> wrote:

    Hello.

    I'm reading the "History of Nautical Astronomy", Mr Cotter describes the state of (apparently insufficient) mathematical literacy of seamen of 15th century like that:

    ...importance in introducing to the English seamen ... the elements of mathematics beyond the golden rule of three.

    What is that?

    Recently I had some hard time guessing what the "butterfly multiplication method" is. We, in Russia, were never tought anything like that.

    Please comment.

    Regards,

    Tony

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