Questions tagged [triangle]

A geometry puzzle centered around the triangle or the centers of a triangle.

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7
votes
1answer
219 views

What percentage of blue? [closed]

Lines are drawn parallel to the base of the triangle, dividing the other sides into 10 equal parts. Every second strip is painted blue. Question What is the percentage of blue color in the ...
25
votes
4answers
3k views

What is the most triangles you can make from a capital “H” and 3 straight lines?

So start with an upper case H, and then draw $3$ straight lines. What is the greatest number of closed triangles that you can form? For example: Note that triangles inside of triangles only count ...
9
votes
3answers
341 views

Special triangles in convex polygons

Given identical 30-60-90 triangles, what is the convex polygon with the highest number of sides that I can build from them? This seems a very easy task by first look, but I’m totally stuck right now. ...
1
vote
1answer
97 views

Can you help me out with this question? [closed]

I found that 3abc+a+b+c formula is correct first and second triangle. But the result for third triangle isn't in the options. Can you find another solution? Source: It's from an old job admission ...
5
votes
2answers
216 views

20 right isosceles triangles into a square

Similar: Unlucky tiling: Arrange thirteen right isosceles triangles into a square Five graded difficulty isosceles right triangle into square tilings Two difficult "Seventeen right isosceles ...
2
votes
2answers
139 views

Two difficult “Seventeen right isosceles triangles into a square” tilings

Similar to: Unlucky tiling: Arrange thirteen right isosceles triangles into a square Five graded difficulty isosceles right triangle into square tilings V.hard problem, 20 right isosceles triangles ...
5
votes
2answers
195 views

Five graded difficulty isosceles right triangle into square tilings

Similar to: Unlucky tiling: Arrange thirteen right isosceles triangles into a square Two difficult "Seventeen right isosceles triangles into a square" tilings V.hard problem, 20 right ...
12
votes
2answers
259 views

Unlucky tiling: Arrange thirteen right isosceles triangles into a square

Link to next puzzle in this series:Five graded difficulty isosceles right triangle into square tilings Two difficult "Seventeen right isosceles triangles into a square" tilings V.hard ...
4
votes
0answers
205 views

2018 January Challenge: Geometry [closed]

Considering it's the beginning of a new year, I have created the following challenge. I hope to make one every month until December 2018! Here goes: Show that $AD-AB>AC^3$. Do not use ...
6
votes
2answers
293 views

Independent Triangles with Straight Lines

Your task is to create independent triangles (which means they do not have the same edge) by drawing straight lines as exemplified below: In this example, there are $5$ lines and $5$ independent ...
0
votes
1answer
256 views

Triangle partial length of hypotenuse [closed]

How can I solve for X? What I did was solve for C, and then took (6/6+2)*C. It seems to work but I am not completely sure. Is there a better way?
1
vote
1answer
113 views

How to map barycentric indices to a single integer? [closed]

how can one map barycentric indices to a single integer? e.g. Edit: added correct image
31
votes
5answers
2k views

Slicing a rectangle

A friend presented this nice little puzzle to me yesterday. You're given a rectangle which is dissected by one of its diagonals, as well as another line that only meets one of the two remaining ...
-1
votes
1answer
193 views

Trianglify the Shapes

For each of the following shapes, draw extra lines to divide the shape into the smallest number of triangles that can completely fill the shape. Example: Solution: Shapes (a correct answer answers ...
6
votes
3answers
1k views

Can you make 10 triangles with just 10 sticks?

Can you make 10 triangles with just 10 sticks? The sticks don't have to have the same length. Hint 1: Hint 2: There are several other possibilities than the one I gave hints for. I recently found ...
3
votes
6answers
901 views

Find the total number of triangles in the diagram

The title of the question says everything $\ldots$ My attempt: We count $2(1+1+1+2+1+1+2+1+1+1+1)=26$ triangles. (On each side $13$ triangles, and then multiplied by $2$). And then we combine them ...
-1
votes
2answers
464 views

That's a lot of triangles

Counting the Triangles in this image individually would take far too long. Can anyone come up with an algorithm to figure out how many triangles are in this shape? Answers should include the number ...
1
vote
1answer
803 views

Four similar triangles

The challenge as described hereafter is to create a total of 4 similar triangles by drawing 4 triangle in a scalene, acute triangle - out of the 5 resulting triangles (4 that make the original one) ...
8
votes
1answer
271 views

The Erasmus tedrahedron

Professor Erasmus has constructed a special tetrahedron that he modestly calls the "Professor-Erasmus-tetrahedron". The professor claims that all four faces of his tedrahedron are right-angled and ...
10
votes
3answers
682 views

The Erasmus isosceles triangle

Professor Erasmus has constructed a special isosceles triangle that he modestly calls the "Professor-Erasmus-triangle". The professor claims that he can cut his triangle into three smaller triangles, ...