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