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Glitch in the matrix (ani.social)

submitted 11 months ago by [email protected] to c/[email protected]

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[–] [email protected] 52 points 11 months ago (3 children)

            
              16 is the right answer if you use PEMDAS only: (8 ÷ 2) × (2 + 2)
1 is the right answer if you use implicit/explicit with PEMDAS: 8 ÷ (2 × (2 + 2))
both are correct answers (as in if you don’t put in extra parentheses to reduce ambiguity, you should expect expect either answer)
this is also one of the reasons why postfix and prefix notations have an advantage over infix notation
postfix (HP, RPN, Forth): 2 2 + 8 2 ÷ × .
prefix (Lisp): (× (÷ 8 2) (+ 2 2))

[–] [email protected] 3 points 11 months ago (1 children)

prefix notation doesn't need parentheses either though, at least in this case. lisp uses them for readability and to get multiple arity operators. infix doesn't have any ambiguity either if you parenthesize all operations like that.

[–] [email protected] 2 points 7 months ago

infix doesn’t have any ambiguity either if you parenthesize all operations like that

There isn't any ambiguity even if you don't.

[–] [email protected] 2 points 7 months ago

16 is the right answer if you use PEMDAS only: (8 ÷ 2) × (2 + 2)

You added brackets and changed the answer. 2(2+2) is a single term, and if you break it up then you change the answer (because now the (2+2) is in the numerator instead of in the denominator).

1 is the right answer

The only right answer

both are correct answers

Nope, 1 is the only correct answer.

this is also one of the reasons why postfix and prefix notations have an advantage over infix notation

Except they don't. This isn't a notation problem, it's a people don't remember the rules of Maths problem.