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17 Dec 2005 - 22:08

## please escort this woman to the roped-off pew

from Anne Dwyer:

How do you know you're obsessed with mathematics education?

When you walk into a used book store and have to buy a Grammar School Arithmetic book published in 1892 because you want to see what math education was like before the progressive movement got involved.

Here are some cool things that I hadn't seen before:

The book teaches how to divide by a fraction (flip and multiply) but it also teaches this method for simplifying a fraction: Reduce 3/4/5/6 to a simple fraction (of course it was written as three fourths over five sixths) The answer: divide the top and bottom by 12 which is the lowest common multiple of 4 and 6 and it reduces to 9/10. I like this method because it works just like getting an equivalent fraction.

A number is divisible by 2 if the last or right hand digit is even.

A number is divisible by 4 if the number denoted by the last two digits is divisible by 4.

A number is divisible by 8 if the number denoted by the last three digits is divisible by 8.

A number is divisible by 3 if the sum of its digits is divisible by 3.

A number is divisble by 9 if the sum of its digits is divisible by 9.

A number is divisible by 5 if its last digit is a 0 or 5.

A number is divisible by 25 if the number denoted by the last two digits is divisible by 25.

A number is divisible by 125 if the number denoted by the last three digits is divisible by 125.

A number is divisible by 6 if its last digit is even and the sum of its digits are divisible by 3.

A number is divisible by 11 if the difference between the sum of the digits in the odd places is either 0 or a multiple of 11.

Well, I have a roped-off pew in the church of my heart for the obsessed.

Edie: An American Biography by Jean Stein

key words: divisibility

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Hmm... Mine's from 1899, and it teaches pencil and paper methods for finding not only square roots, but also cube roots thru fifth roots, in sufficient detail that you can see the pattern to extend it to sixth roots and beyond.

Mine's an International Correspondence School text.

P.S. I also was in a used book store this weekend, and I also purchased some dated math texts (linear algebra and diff eq). :) But I am neither a math educator nor a parent, just obsessed I guess.

-- KtmGuest - 19 Dec 2005

But I am neither a math educator nor a parent, just obsessed I guess.

That's great!

You can sit in the roped-off pew with the rest of us!

-- CatherineJohnson - 19 Dec 2005