4 votes

8x8 Grid with no parallels

It's fairly simple to prove an upper bound of:
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  • 3,460
4 votes
Accepted

8x8 Grid with no parallels

I'm using a $9 \times 9$ matrix, with $1$ if there is a point and $0$ otherwise.
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  • 7,429
3 votes

How high does the ladder reach up the wall?

Let h,w be the height and width of the triangle formed by the ladder with the wall and the ground. First let us divide through with d: $H:=h/d, W:=w/d, L:=l/d, D:=d/d=1$ Then $L^2=H^2+W^2$ (1). ...
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2 votes
Accepted

Two triangles in a circle

The answer is intuitively clear: Formal proof is also not all that difficult:
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2 votes

A donut, a piece of string and a pair of spectacles

I also believe your puzzle is impossible. Let's simplify the puzzle a bit more. If you rotate the left red (elongated) torus half a turn and merge the holes of the red tori you get something like ...
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  • 19.3k
1 vote

Two triangles in a circle

Cut a square out of the circle. Divide it in the diagonal to make two equal triangles. Area of circle: $\pi r^{2}$ Diagonal of square: Side of square: Area of square: Part of square in the circle:...
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1 vote

Complete sets of pictures by replacing blanks

Partial answer
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