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Basic Math - Mathmatical Reasoning
Expert: John Zalewski - 10/7/2008
Question
Why does the left to right rule mean that you don't always do multiplication before division or addition before subtraction?
Answer
Hello, Raven.
This is the phrase to remember: Please Excuse My Dear Aunt Sally.
P is for Parentheses, E is for Exponents, M is Multiplication, D is for Division, A is for Addition, and S is for Subtraction.
Parentheses and exponents always come before the last four. However, multiplication and division are actually grouped together, as are addition and subtraction.
In actuality, it reads "Parentheses Exponents (Multiplication and Division) (Addition and Subtraction)."
Division is done before multiplication, or subtraction before addition, if they are further left in the problem.
For example, in the problem 5/5x6, the answer is 6. First, you have to divide 5 by 5, getting an answer of 1, and then multiply 6 by 1, giving you 6.
Hope this helps.
Regards,
John
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