Thread: 6÷2(1+2) = ? View Single Post
January 4th, 2013, 03:08 PM   #262 (permalink)
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Quote:
 Originally Posted by MoodyBlues Someone please feel free to correct me if I'm remembering this wrong--after all, it was back in 1982 that I took College Algebra. There shouldn't be any ambiguity about this equation because you're supposed to solve the contents of parentheses first, hence we do the (1+2) to get 3. Then, since the remainder of the problem involves division and multiplication, we simply go from left to right to solve it. We have: 6 / 2 * (1 + 2) or (6 / 2) * (1+2) or (6 / 2) * (3) or (3) * (3) for an answer of 9. Right...?
Yep, you are 100 percent correct. Under standard decimal arithmetic, that is the procedure to use. Many people learn the acronym PEMDAS, or the phrase "Please Excuse My Dear Aunt Sally", and incorrectly learn or assume that multiplication has higher precedence than division. Under standard rules of arithmetic, multiplication and division have the exact same precedence and must be computed from left to right. Addition and subtraction also have the same precedence and also should be completed from left to right.

This is why when I teach this topic, I prefer to use the phrase "Please Exclude Mom or Dad As Sane". It gets a chuckle out of people and also inserts the idea that it's M or D, not M then D.
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