| Discussion: | All Topics |
| Topic: | PEMDAS |
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| Subject: | RE: PEMDAS |
| Author: | KT8 |
| Date: | Dec 1 2007 |
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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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