Re: Why does PEMDAS do multiplication and division before addition and subtraction? Message #12 Posted by Kimberly Thompson on 30 July 2013, 8:40 a.m., in response to message #1 by Don Shepherd
Don
Interesting read on the Math Forum at this url...
http://mathforum.org/dr.math/faq/faq.order.operations.html
The order of operations in which one is to interpret a mathematical expression such as "2+3 * 5" is a convention. This means that a long time ago, people just decided on an order in which operations should be performed. It has nothing to do with magic or logic. Some people decided to adopt a way, and it has stuck ever since. It just makes communication a lot easier.
Another way of saying this is that rather than being inherent in the structure of mathematics, the concept of "order of operations" is a matter of mathematical notation. Order of operations refers to which operations should be performed in what order, but it's just convention. The notation tells you which operations to do first, not something about the underlying mathematics.
..continued at this url...
http://mathforum.org/library/drmath/view/57289.html
The PEMDAS convention currently taught in schools, ... tells us ... as long as we're working with people who also follow that convention, we can leave the grouping symbols out. That doesn't seem like such a big benefit, but if you're writing hundreds or thousands of expressions each day, then those little savings can add up.
This particular convention is optimized to make it possible to write polynomials without grouping symbols.
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