How many triangles can you see? Animated answer - Melissa Maths

Triangle problem. Count the triangles and share how many you can see but pause the video before the answer of how many there are in total is revealed!

[reznovvazileski]

Per layer I count 4 singles+3 doubles+2 triples+1 MoaT so we've got 10 per layer. Any lower vertical layer can only be made a triangle by including the tip or it becomes trapeze. That in mind the same process repeats 4 layers in a row giving us 4*10 = 40.

[gonzalotapia]

Every row has the 4+3+2+1 = 10 combinations.
Then it's 4*10= 40 triangles

[OrenLikes]

there are 5 diagonals and you need to choose 2, there are 4 horizontals and you need to choose 1:
5C2*4=10*4=40

[youcanteachthem]

If I knew this video existed, I wouldn't have created my own version of this animation. Except that I didn't upload it to YouTube.
You inspire me to create some silent videos.
Thank you and well done :)

[potaatobaked]

Let’s see. There is 4 different triangle heights. There are 4 choices for containing no vertical internal lines, 3 for 1 vertical internal line, two for 2 vertical internal lines, and 1 for 3 vertical internal lines, so this is 4 * (4+3+2+1) or 40

[lousyman]

The most interesting aspect of this question to me is - Is it really ok to count the same pieces multiple times?

[xlerb]

I got 40, and the reasoning that that was all of them was sound and I knew it was sound. But I still spent a bit looking for the sneaky extra one(s) before I played the video.

[MelissaMaths]

Thank you for all your fabulous discussions about this video. I never expected it to get this much attention, and I love that it is entertaining so many people. 😘 Melissa

[THall-vicp]

Well, I'm glad I got it right. I wasn't sure and thought maybe there was some trick answer.

[sciencegremlin]

Every object after the first 4 triangles has an interior angle greater than 180 degrees so not triangles.

[bernardoomar]

40 but if you rotate the triangle then 40x 3= 120 combinations

[patrickcorliss]

I got 47. Must have double counted some.

[MP-tfcc]

I count from largest to smallest, 40.

[benjaminmathew]

U missed a few for example the middle line divides the biggest triangle into 2 smaller right trangkes 😊

[callyral]

please include captions saying "[Silence]" so i won't think something is wrong with my phone

[joakimsiljelind]

The question is "How many triangles can YOU see?" - Well what I see is most likely something I can see... 😂