# Math problem: 1+1=0 [duplicate]

See if you can solve this math-problem:

$$\begin{bmatrix} 1&+&1&=&0\\ 2&+&8&=&2\\ 2&+&2&=&0\\ 9&+&8&=&3\\ 3&+&4&=&0\\ 6&+&9&=&2\\ 0&+&2&=&1\\ 9&+&3&=&? \end{bmatrix}$$

Best of Luck!

Ps: Here is the link without brakets and here is one without latex

• If you can't see the $\LaTeX$(latex) commands It is here in normal symbols: Jul 23, 2020 at 11:20
• 1+1=0 2+8=2 2+2=0 9+8=3 3+4=0 6+9=2 0+2=1 9+3=? Jul 23, 2020 at 11:22
• $1+1=0\\2+8=2\\2+2=0\\9+8=3\\3+4=0\\6+9=2\\0+2=1\\9+3=?$ Jul 23, 2020 at 11:24
• I'm sure I've seen this idea on this site before but can't find the dup. Jul 23, 2020 at 11:35
• @hexomino This is the closest I've been able to find - quite a different question using the same general concept at its core. Not convinced it's close enough for a dup...
– Stiv
Jul 23, 2020 at 11:47

$$9+3=1$$
In each case, what's being added together here is the number of 'closed counters' (i.e. the 'holes' in the numbers) when the numbers are written out on a standard 7-segment calculator display1. The digit 9 has one closed counter, while 3 has zero. The sum is thus 1.

1 This should rule out any queries surrounding the number '4', which can be considered to have 1 or 0 closed counters in different typefaces.

• Yes you are right. Jul 23, 2020 at 11:29
• What about the digit $4$? Jul 23, 2020 at 11:29
• Just beat me to it!!! Jul 23, 2020 at 11:30
• Good answer, but then it depends on how one would write the 4, no? Here 3 + 4 = 0, not 1. Maybe that’s just a typo/quirk... (+1) Jul 23, 2020 at 11:30
• @JaapScherphuis El-Guest and others: My latest edit should overcome this issue...
– Stiv
Jul 23, 2020 at 11:34

Is the answer 1 because 9 equals 1 and 3 equals 0 and so 9 add 3 equals 1

• I hate my life I literally worked this out in less than a minute, I just went on stack exchange after this puzzle was put on 17 mins ago swear I have the worse luck on here! Jul 23, 2020 at 11:34
• This should be a much more reasonable answer, only involving arithmetic and not strange interpretations of the values. Jul 23, 2020 at 12:36

My Math logic


Since 1+1=0 and 2+2=0, I assume that adding the same number gives me zero.
We also have 0+2=1, meaning that 0+x=1
9+3 = ?, but we know that 9+8=3, so we can reach this form
9+3 = ?
9+(9+8) = ?
9+9+8 = 0+8 = 1