Discussion:  All Topics for Patterns and sequences 
Topic:  PEMDAS 
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Subject:  RE: PEMDAS 
Author:  KT8 
Date:  Dec 1 2007 
More thoughts on O of O:
I teach 7th and 8th grade gifted students and they are pretty familiar with
"PEMDAS," but I teach them that it is now time to get more sophisticated than
the simple operations represented by that acronym. They learn that P stands for
"grouping symbols," including the fraction bar, absolute value bars and
radicals, in addition to parentheses and brackets. And that "exponents" includes
fractional exponents  ie, square roots and cube roots. Because they should
understand by now that multiplication and division are inverse operations and
any division problem can be written as a multiplication problem, they "get"
working from left to right with MD and AS.
Where students have the most trouble is remembering that 2^2 equals 4, and
that's because of order of operations. You do the exponent first (2^2=4), then
take it's opposite, ie, multiply by 1.
When they're entering long expressions into a graphing calculator, they don't
always realize that they need to put parentheses around an expressions that were
above and below a fraction bar in a handwritten problem. Ex: (4+2)/(3+7) is not
equal to 4+2/3+7 or (4+2)/3+7. The original problem would have looked like
this:
4+2
____
3+7
(That's the best I can do in "text only" format).
 
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