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 $\bf{3+3 ?}$

  • $\begingroup$ Everyone has gotten into the craze... now we just need Gareth $\endgroup$ – Quintec Dec 19 '17 at 12:26
  • $\begingroup$ The arrangement just makes my head scream from the obvious patterns there :) $\endgroup$ – Wen1now Dec 19 '17 at 12:29
  • $\begingroup$ I wonder what would happen if I just answered ‘6’ :P $\endgroup$ – Beastly Gerbil Dec 19 '17 at 13:30
  • $\begingroup$ @BeastlyGerbil without an explanation it’d get flagged :) $\endgroup$ – Rubio Dec 19 '17 at 13:31

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


  • 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 '17 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 '17 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 '17 at 14:42
  • $\begingroup$ @Lolgast I assume the 9 here is the version without the bottom segment lit up. $\endgroup$ – Volatility Dec 19 '17 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 '17 at 2:48

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