[Edu-sig] Re: reducing fractions

Steve Litt slitt@troubleshooters.com
Fri, 15 Sep 2000 11:14:50 -0400

At 12:41 PM 8/14/00 -0700, Kirby Urner wrote:
>"Janet Johnson" <johnsonje@adelphia.net> wrote:
>>I teach 6th grade and every year my students seem to have a lot of
>>difficulty with fractions, specifically, reducing or recognizing that a
>>fraction isn't reduced.  I have given them many ideas on how to tell, even
>>to the point of writing out the factors for both the numerator and
>>denominator.  Does anyone have any suggestions on how to get this concept
>>across to the students?  Any suggestions would be greatly appreciated.
>>Janet Johnson
>You could unsimplify some fractions e.g. 2/3 -> 10/15
>i.e. show the inverse of what it means to "simplify".
>If 'prime number' is already a concept, you could try 
>'relative prime' meaning no factors in common (i.e. 
>"a fraction is in lowest terms when the numerator and
>denominator are both integers and are relative primes").
>Along these lines, I really like your idea of writing 
>out the prime factors, crossing out those in common e.g.:
>   150/210 -> (3 x 5 x 2 x 5) / (7 x 3 x 2 x 5) -> 5/7

That's how my 7th grade teacher taught me to simplify fractions, and I've
never been sorry.

Steve Litt
Webmaster, Troubleshooters.Com