This is an interactive version of the puzzles that appeared in Alex Bellos's 24th June column in The Guardian. They were originally suggested by Donald Bell, a former director of the National Engineering Laboratory.
Puzzle 3: solution 2 was found by n4blue, solutions 3 & 4 were found by HarryP81, and solutions 5, 6 and 7 are by "Reg" (AKA, a brute force search).
If at first you don't succeed: try, try, try-angle again....
Rearrange these 30-60-90 triangles so they have a line of symmetry. No cheating with overlaps.
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In Manhattan, the closest you can get to a 30-60-90 triangle is a tetromino.
Rearrange these ones so there is a line of symmetry.
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rotate
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Flipping hell - and some more!
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rotate
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A needle in a haystack. These are tetrominos with one square deleted; they're called tetrominos.
Trominos are symmetrical so it's easy to arrange them in a symmetrical pattern. Ignore the obvious solutions. Find solutions that don't use the line symmetry of any tromino; i.e. align the trominos vertically and horizontally so that there's a vertical or horizontal symmetry.
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rotate
Tap or click to switch to rotating pieces.
Tap or click to switch to moving pieces.