Math CentralQuandaries & Queries


Question from Ross, a student:

48 ÷ 2 (9+3)

Is the answer 2 or 288?

Hi Ross,

I am going to copy what I wrote to Steve a while ago.

These problems annoy me as much, or even more than they annoy you. No mathematician or anyone who uses mathematics would ever write this expression. Mathematical notation should be clear and unambiguous, which this is not. You don't want to read my diatribe but this question reinforces the idea that mathematics is some ritualistic endeavour where you have to make special incantations before you start, "BEDMAS", "PEDMAS", "FOIL", "CAST" or some other acronym.

By a strict reading of PEDMAS you divide before you multiply so this becomes $24 \times (9+3)$ which is $288,$ but if you were one of my students and wrote this expression I would give it back to you and tell you to use parentheses to make the expression clear.


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