At some point, there may be two valid solutions. (actually three: one obvious, one less, third one even less.)

Edit: actually four solutions, one found by Foitn & Saeïdryl, which is very related to the even less obvious one. There's a hint for the even less one in the picture.

Edit2 : @123 found the most absolute answer of all time in comments!

enter image description here


Vertices are geometric immaterial points. What about pixels?


Triangles need absolutely three vertices. Everything depends on what smallest green light emitting material you chose to relatively set as one vertice. Answer is between 3(obvious) / 8(rgb mix) / none (pixels are not triangles) / none (green is a very personal perception) / a finite computable lot of possibilities (each powered pixel emits green light, even black ones) / a finite googleplexsquared djillion possibilities if you chose unpowered baryonic matter emitting green light inbetween pixels too / another close to infinity probability if you print the image and count green emitting particles aswell / and some small to very big infinity if you add imaginary vertices, if you go fractal, if you count electronic positions' probability relative to time, over and over, until universe's heat death. Everything is absolutely relative, so sometimes it's easier to say there are 3 green triangles, even if any other answer is correct.

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    $\begingroup$ Logical deduction AND lateral thinking? That's an odd combination.... $\endgroup$ – North Mar 15 '18 at 13:57
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    $\begingroup$ @North So, that's "lateral deduction" - the same approach banks use when they deduct fees from our accounts. ;-) $\endgroup$ – Phylyp Mar 15 '18 at 13:59
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    $\begingroup$ Wow, thats VERY lateral, indeed. $\endgroup$ – North Mar 15 '18 at 14:03
  • $\begingroup$ @North since everything is absolutely relative, blending both is possible! $\endgroup$ – qq jkztd Mar 15 '18 at 14:09
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    $\begingroup$ I agree with "put on hold as too broad" $\endgroup$ – qq jkztd Mar 15 '18 at 16:06

Well based on the previous riddle How many rectangles are in this image?:

No triangle, since they are composed of tiny squares, then you cannot form triangles from squares.

  • $\begingroup$ This made me LOL, nice lateral thinking answer. (I'm not the downvoter, btw) $\endgroup$ – Phylyp Mar 15 '18 at 13:54
  • $\begingroup$ Well lateral-thinking tag is present and that was the whole point of his previous and first riddle 2h ago, we can think this one is on the same thinking. And that was the fastest downvote ever, I posted it and... "-1" <.< $\endgroup$ – Saeïdryl Mar 15 '18 at 13:56
  • $\begingroup$ You found a fourth upvoted answer! (neither am I the downvoter...) $\endgroup$ – qq jkztd Mar 15 '18 at 14:05
  • $\begingroup$ Wow, I really like that answer, my thought is that that is the even less obvious one, which I've added to my own answer (I gave you credit :P), +1 for you man! $\endgroup$ – Foitn Mar 15 '18 at 14:09

The obvious answer:

3 green triangles

The less obvious answer:

3 green trianges + 2 cyan triangles + 1 yellow triangle

Since green (primary colour) is a component of cyan and yellow according to the additive (RGB) colour model.
Thanks to Gareth McCaughan for the correction!

The least obvious one:

3 green trianges + 2 cyan triangles + 1 yellow triangle + 2 white triangles

Since white is a combination of red, green and blue.

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    $\begingroup$ You have that the wrong way around. Green is a component of cyan and yellow in the RGB model (C=G+B, Y=G+R); it's made out of cyan and yellow in the CMYK model. $\endgroup$ – Gareth McCaughan Mar 15 '18 at 13:51
  • $\begingroup$ Many thanks, @GarethMcCaughan I've corrected that. $\endgroup$ – Phylyp Mar 15 '18 at 13:53
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    $\begingroup$ green is a component of every colour in the image though. $\endgroup$ – 123 Mar 15 '18 at 13:54
  • $\begingroup$ @123 - very interesting twist, given as we're all probably seeing this via RGB pixels. :-) $\endgroup$ – Phylyp Mar 15 '18 at 13:55

Alright I'd say (based on my previous answer and Saeïdryl his answer):

The obvious one:

3, since there are three truely green triangles in there

The less obvious one:

9, three of them are truely green, 2 are cyan, 1 is is pink, which both contain a green element and 3 white, which of course contain all three of Red, Green and Blue (RGB)

The even less obvious one (Thanks to Saeïdryl):

None at all, since these are pixels, which are squares, there are no true triangles, because you cannot create a triangle from squares.

The fourth one:

When looking at the triangles, we can divide these up into smaller triangles, which makes that there are a lot (would take me a long time to calculate actually) of triangles up. Going even further, you could say (not sure though) that one pixel is one triangle, thereby saying that each pixel in the image that contains green is a green triangle.


As a counterpart to @Saeïdryl's answer:

There are uncountably many triangles, even inside one single square pixel. The green "triangle" in the picture below isn't a real, mathematical one, because it's composed of 11 pixels. 14 real mathematical triangles are displayed inside it, though. They're displayed in red with a black stroke as an example, but they'd still be here if they were green without stroke. Just like a straight line is an infinite set of points, a filled shape can be considered as the union of infinitely many shapes: enter image description here

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    $\begingroup$ I don't get the "uncountable" part. You seem to be taking into account all the potential triangle boundaries that one could draw inside of a space? If I hand you a blank sheet of paper, it displays 0 triangles. It's a pretty big stretch to go from "I could draw any number of triangles" to "there are an infinite number of triangles displayed". You can imagine anything you want, but that doesn't really have any bearing on what's actually displayed. By that logic, the picture displays the Pope scoring the winning touchdown at the Super Bowl... an infinite number of times. $\endgroup$ – Nuclear Wang Mar 15 '18 at 15:24
  • $\begingroup$ @NuclearWang: You're correct with the Pope ;) I'd say a blank sheet of paper has indeed 0 triangles, but a sheet of paper with one filled square has infinitely many triangles, popes and circles on it, yes. $\endgroup$ – Eric Duminil Mar 15 '18 at 15:34

I would say



3 are obvious (with RGB values left bottom:(0,255,0) and top and right one :(0,255,1)


if I do a select all and Ctrl+Shift+i (in out beloved MS Paint) for inverting colours, I get this: inverted image

we have one more with RGB:(0,255,1)


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