Abraham Lincoln and the Rule of ThreeDate: 04/13/2003 at 19:53:33 From: Alex W. Subject: Mathematics In the biography of Abraham Lincoln he states that he learned to "read, write, and cipher to the rule of 3." Can you please explain the phrase "cipher to the rule of 3"? Date: 04/14/2003 at 10:50:27 From: Doctor Rick Subject: Re: Mathematics Hi, Alex. It appears that "read, write, and cipher to [or, as far as] the Rule of Three" was something of a standard phrase in the nineteenth century. On the Internet I found this problem, said to come from the National Council of Teachers of Mathematics: In his 1859 autobiography, Abraham Lincoln wrote, "Of course when I came of age I did not know much. Still somehow, I could read, write, and cipher to the Rule of Three." The rule of three was a historical form of a proportion. To cipher to the rule of three for 3, 9, and 2 is to complete the phrase "3 is to 9 as 2 is to ___," with the answer being the quantity 6. In other words, ciphering to the rule of three is to solve a proportion such as 3/9 = 2/x, where x=6. Cipher the rule of three for 4, 6, and 3. Cipher the rule of three for a, b, and c. Lincoln was saying that his math education ("ciphering" means basically "working with numbers") went as far as learning to solve problems with proportions. - Doctor Rick, The Math Forum http://mathforum.org/dr.math/ Date: 04/14/2003 at 11:21:16 From: Doctor Peterson Subject: Re: Mathematics Hi, Alex. If you are interested in the details of this method, you can search our archives for the phrase "rule of three". Here is one explanation: Rule of Three http://mathforum.org/library/drmath/view/60822.html If you have any further questions, feel free to write back. - Doctor Peterson, The Math Forum http://mathforum.org/dr.math/ |
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