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Please Excuse My Dear Aunt Sally

Posted by Bruce Kahl on July 24, 2000

In Reply to: Aunt Sally ?! posted by kts on July 24, 2000

: Does anyone know what an 'Aunt Sally' list is ?

In a former life back in the late sixties thru the mid eighties I taught mathematics to junior high school children in NYC, Bronx and Brooklyn.
The only Aunt Sally thingy I know has to do with mathematics.It is a mnemonic aid.
Please Excuse My Dear Aunt Sally.

Parentheses
Exponents
Multiplication
Division
Addition
Subtraction

This mnemonic helps us remember which order to complete mathematical operations. The order in which a problem is solved is crucial. Without having a set order, we would arrive at different results.

2 + 3 x 6

Is the answer 30? 2 + 3 = 5 5 x 6 = 30??
Wrongo!!!

This is why we need to learn the mnemonic Please Excuse My Dear Aunt Sally. If not, we would not know the correct answer to the above is 20!

The answer is 20. Our mnemonic tells us which order to solve the problem. We do not just read left to right as if it were an English sentence. Multiplication comes before addition in the mnemonic (My comes before Aunt), therefore, we must multiply before we add.

If we do that, then the answer is 20! 3 x 6 = 18. 18 + 2 = 20.