420

submitted 11 months ago by Toes@ani.social to c/196@lemmy.blahaj.zone

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[-] cerement@slrpnk.net 52 points 11 months ago

        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))



      

[-] brian@programming.dev 3 points 11 months ago

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.

[-] SmartmanApps@programming.dev 2 points 8 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.

[-] SmartmanApps@programming.dev 2 points 8 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).