7
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Yup, I'm adding yet another Simple Math Problem to the recent trend.
Here ya go!


Given that: $$\begin{array}{ccccccc} \begin{array}{c} 1-1=0\\ 1+1=2\\ 1+6=7\\ 2+5=7\\ 5+1=6\\ 6-5=1\\ 9-7=2 \end{array}&~~~& \begin{array}{c} 1+3=5\\ 2+2=5\\ 2+3=6\\ 3-1=3\\ 4+2=7\\ 6+0=7\\~ \end{array}&~~~& \begin{array}{c} 4-1=2\\ 4+1=4\\ 8-4=3\\ 8+0=7\\~\\~\\~ \end{array}&~~~& \begin{array}{c} 1+2=6\\ 5+5=5\\ 7+1=3\\ 8-7=4\\~\\~\\~ \end{array} \end{array} \\~\\$$

What is $\bf{3+3 ?}$

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4
  • $\begingroup$ Everyone has gotten into the craze... now we just need Gareth $\endgroup$
    – Quintec
    Dec 19, 2017 at 12:26
  • $\begingroup$ The arrangement just makes my head scream from the obvious patterns there :) $\endgroup$
    – Wen1now
    Dec 19, 2017 at 12:29
  • $\begingroup$ I wonder what would happen if I just answered ‘6’ :P $\endgroup$ Dec 19, 2017 at 13:30
  • $\begingroup$ @BeastlyGerbil without an explanation it’d get flagged :) $\endgroup$
    – Rubio
    Dec 19, 2017 at 13:31

1 Answer 1

5
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The calculations are made by

considering the digits on a 7-segment display, adding or subtracting the lit segments as appropriate, then counting the number of lit segments in the result.

Edit: I may have been a bit vague above. Think of "adding" as overlaying the two digits, and "subtracting" as the second digit masking the first. In the case of addition, this is different from adding the number of lit segments for each digits, as there may be some overlap between them.

Therefore, 3 + 3 is

5

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5
  • 1
    $\begingroup$ No matter how I think of this, I can't seem to get it to work... 3 has 5 segments, so that gives 10, which in turn gives 8 segments, no? (sorry, no spoilers in comments...) $\endgroup$
    – Lolgast
    Dec 19, 2017 at 14:18
  • $\begingroup$ @Lolgast I guess I didn't really explain it well. I've updated my answer, hopefully it's a bit clearer. $\endgroup$
    – Volatility
    Dec 19, 2017 at 14:37
  • $\begingroup$ Ah I think I got it now. However, 9-7=2 doesn't seem to fit? Shouldn't it be 9-7=3? (Unless it's considered 9+9=5, which doesn't quite match the 9+9=6 what I was expecting...) $\endgroup$
    – Lolgast
    Dec 19, 2017 at 14:42
  • $\begingroup$ @Lolgast I assume the 9 here is the version without the bottom segment lit up. $\endgroup$
    – Volatility
    Dec 19, 2017 at 14:50
  • $\begingroup$ I even thought of 7-segment; in fact that was pretty much the only thing I tried. If only I'd done it with pen and paper instead! +1 $\endgroup$
    – Wen1now
    Dec 20, 2017 at 2:48

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