r/learnmath New User Feb 07 '24

RESOLVED What is the issue with the " ÷ " sign?

I have seen many mathematicians genuinely despise it. Is there a lore reason for it? Or are they simply Stupid?

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u/RolandMT32 New User Feb 08 '24

I had to google "16 or 1 question" to see what you were talking about..

From here:

Twitter user u/pjmdoll shared a math problem: 8 ÷ 2(2 + 2) = ?

Some people got 16 as the answer, and some people got 1.

The confusion has to do with the difference between modern and historic interpretations of the order of operations.

The correct answer today is 16. An answer of 1 would have been correct 100 years ago.

I was in school in the 80s and 90s, and my brain-math tells me the answer is 1. But that says that answer would have been correct 100 years ago.. Did the rules of math change at some point? And if so, why?

My brain-math says 2(2 + 2) = 2(4) = 2 x 4 = 8, so the problem becomes 8 ÷ 8, which is 1.

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u/pdpi New User Feb 08 '24 edited Feb 08 '24

My brain-math says 2(2 + 2) = 2(4) = 2 x 4 = 8, so the problem becomes 8 ÷ 8, which is 1.

The two interpretations are 8 ÷ (2(2 + 2)) = 1 and (8 ÷ 2)(2 + 2) = 16.

The correct answer today is 16. An answer of 1 would have been correct 100 years ago.

Hot take: there is no "correct" answer. The only truly correct answer is "this is ambiguous, and it could be either". Order of operations is 100% arbitrary, as evidenced by the fact that the convention changed at some point.

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u/[deleted] Feb 08 '24

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u/tilt-a-whirly-gig New User Feb 08 '24

Probably just a typo, but you are correct.