How many triangles do you see?

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Originally published at: https://boingboing.net/2020/01/30/how-many-triangles-do-you-see.html

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I see nine.

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18?

I keep thinking I am missing some though.

ETA and now done with the Popular Mechanics article and indeed 18.
Well I thought it was pretty straight forward but when posed as a brain teaser I want to over think it.

ETA More now that I can get to the meme site.

image

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Same here. Almost sure it’s 18.

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Does it still count as a ‘triangle’ if there is a line segment connecting the midpoints of two sides?

Or is that just a trapezoid that shares a side with a triangle?

But, yeah, I get 18.

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18
…

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18, unless the lines on the paper also count, then … lots.

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I SEE all of them…

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A triangle is a figure with 3 straight edges. All the straight lines in this picture are parallel. No triangles here. QED.

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I got 16 initially, read the comments here, had to go back and figure out which two I had missed, yep 18.

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One large triangle containing lines, and 3 interior triangles within those lines. To find more you have to imagine some lines don’t count as lines.

That’s my contrarian opinion and I’m sticking to it.

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But nobody will agree.

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Yep. The enclosed form’s lines aren’t straight. So, I also see no triangles.

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How many circles do you see here?
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I would say “three” but if I’m reading your opinion right, the orange circle is no longer a circle because there’s something inside it. Are you sticking to it?

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36
(and some filler for the comment)

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I get 20 in a somewhat sneaky way:

18 as illustrated in the pop mech solution, Plus two small triangles found in the capital letters A in the question.i

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Did you include the horizontal lines which turn each of the other triangles into 3 triangles

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Laurel. No, white and gold!

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Looking at the drawn on lines there are 18. I’m getting an additional 30 give or take when you incorporate the ruled lines. So 48 ish

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The answer is actually 20.

Don’t forget to count the capital As.

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