Lesson 4: Numeric Proportionality. History of the Rule of Three (III)

March 31, 2011

The Rule of Three

The rule of three was a name given in earlier days to an algorithm for solving proportions. The method required setting up the problem so that the unkown quantity is always last “extreme” in the proportionality. In  http://www.pballew.net/arithm18.html you can see an image that shows the rules as given by a 1827 arithmetic.

This rule is covered in almost all the arithmetics up to the beginning of the 20th century.

The rule of three was such a common part of arithmetic education that it found its way into common expressions. In his autobiography, Lincoln writes that he that he learned to “read, write, and cipher to the rule of 3.” A poem often used in student copy books was:

Multiplication is vexation;
Division is as bad;
The Rule of Three doth puzzle me,
And Practice drives me mad


Abraham Lincoln 16th President of the United States, 1809 – 1865 In 1865 Lincoln was assasinated as he watched a play

Could you translate it into Spahish?

This extra work will give you an extra point in this lesson!


From  http://www.pballew.net/arithm18.html


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