Search All of the Math Forum:
Views expressed in these public forums are not endorsed by
NCTM or The Math Forum.



Lowest common denominator endangered?
Posted:
Jan 2, 2005 4:40 PM


The book I'm reading gives the algorithms for adding and subtracting fractions:
a/b+c/d=ad+bc/bd and similarly for subtraction. It notes that this "does not necessarily give you the LCD". They do mention 4 methods for obtaining the LCD "if desirable". That "if desirable" phrase appears three times. It never mentions *how* desirable finding the LCD is, and the whole section on it seems to be an afterthought. Given the emphasis on calculators in the book, I'm wondering if the LCD is still an issue, or is it considered nice to know, but don't spend alot of time having child memorize how to find this. What is the current thinking on LCD and does it come up on the standardized testing everyone is barking about? I have no memory of being taught fractions, and, when I put myself to a set of them, I found I used a combo of good guess and reduction after calculating, with a pinch of prime numbers sprinkled over the good guess. Not a method given to methodical instruction. TIA blacksalt
 submissions: post to k12.ed.math or email to k12math@k12groups.org private email to the k12.ed.math moderator: kemmoderator@k12groups.org newsgroup website: http://www.thinkspot.net/k12math/ newsgroup charter: http://www.thinkspot.net/k12math/charter.html



