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I just began filling out a survey for a contest that Walmart is hosting. Since I live in Canada there is a skill testing question which was as follows: $$(4×2)+(6/3)?5=$$ The answer to the equation was omitted.

What kind of mathematical significance does the question mark hold?

I have tried Googling the equation for an explanation, but to no avail.

Is the equation bunk?

FWIW, the answer turned out to be 5... so obviously the question mark represented a subtraction symbol, but how was I ever supposed to induce that if the answer is/was omitted?

epimorphic
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oldboy
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    I guess that a symbol did not render and was replaced by a question mark. – Sri-Amirthan Theivendran May 27 '17 at 22:02
  • Please don't re-post on-hold/closed questions. I'm sure it's no different on SO. – epimorphic May 27 '17 at 22:57
  • @epimorphic i apologize. i was quite frustrated by the fact that an experienced member edited my question so that it was not even true to the original question and then voted to put the question on hold because it was unclear... such an amazing first experience on this stackexchange lol – oldboy May 28 '17 at 01:14
  • @FoobazJohn Thanks, you're probably right. – oldboy May 28 '17 at 01:26
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    Further to what @FoobazJohn commented, there are multiple characters that look like a minus sign - 'hyphen', 'en-dash', 'em-dash' just to name a few - and rendering these correctly depends on the encoding being set correctly everywhere. It'd be easy for a mistake to happen, and un-recognized characters are ofter rendered as either an empty box or a question mark. I'm betting that's what happened. – JonathanZ May 28 '17 at 04:26

1 Answers1

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If you know the answer is $5$, then you can guess that the $?$ is supposed to be a minus sign. Conversely, if you know that the $?$ is supposed to be a minus sign, then you can compute that the answer is $5$.

Without one piece of information or the other, you don't have much to go on. But in hindsight, you could reason as follows:

  1. The $?$ is a binary operator. Since there is no well-known operator rendered as a question mark, it is probably a rendering error.
  2. It is probably one of the elementary-school binary operators: $+$, $-$, $\times$, or $\div$ aka $/$.
  3. The operators $+$, $\times$, and $/$ are already used in the expression, so we know that they were able to render those symbols. But $-$ is not used elsewhere, so it remains possible that they couldn't render that symbol.
  4. In a silly contest of this kind, they probably wouldn't repeat a symbol. Instead, they would try to use every operation the reader might know about. Again, by elimination, this suggests $-$.
  5. The symbols $+$ and $/$ are part of ASCII, and they're unlikely to be corrupted. There is a hyphen "-" and a letter X in ASCII, but a true minus sign or multiplication sign is a more advanced symbol, which is more error-prone. This again suggests either $-$ or $\times$.

Considering 3, 4, and 5, you have pretty good evidence that it was supposed to be a $-$. It's enough evidence to make a best guess, at least.

Chris Culter
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  • Exactly my point. Both the answer to the equation and whatever the question mark was supposed to represent were omitted from the question :/ Hm... but webpages aren't written in binary? Or am I misunderstanding you? – oldboy May 28 '17 at 01:25
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    The question was probably written by person A at some public relations firm, then emailed to person B at Walmart, who opened the email using a different OS and a different web browser than person A. Then B retyped it into a word processing document and faxed it to intern C, who scanned it, copy-pasted it into a text message, and sent it to person D, who received the text on a 10-year-old flip phone, printed it out, scanned it, and sent the scan to the printers at print company E, who prepared a master paper copy, and scanned that with OCR software into webpage F. – Chris Culter May 28 '17 at 01:30
  • lolllllllllllll – oldboy May 28 '17 at 01:33