# Is this Tetris puzzle solvable?

As a birthday present last year, I received some fridge magnets. They didn't come as a puzzle, so I don't know if they have a solution, but I made a puzzle out of them anyway.

The magnets are tetrominoes. There are 7 of each shape. Is it possible to arrange them into a 7x28 rectangle so that they are all used and all inside the rectangle?

The closest I have managed is this:

• As an aside, just because it's a puzzle doesn't mean it has a solution; the 15 puzzle, for example, had a popularized unsolvable configuration.
– user1502
Commented May 28, 2015 at 8:58
• If you want a solvable challenge, use these pieces to build a 12x16 rectangle (there will be one left over). Commented May 28, 2015 at 14:22
• Thank you to the upvoters! This question has just become my biggest SE achievement as 'the highest voted question on the site' Commented May 29, 2015 at 7:23
• en.wikipedia.org/wiki/… Commented May 29, 2015 at 14:21
• You've got an odd number of "T"s, so no, not possible.... Oh, I see @Tryth already go it. Commented May 29, 2015 at 15:06

Let the $$7\times 28$$ area be painted with black and white squares in a checkerboard pattern. Every piece will cover $$2$$ black and $$2$$ white squares, except the T-piece, which covers $$3$$ of one color and $$1$$ of another. Since there are $$7$$ T-pieces, a tiling that uses every piece cannot cover the same number of black and white squares. Since the board contains the same number of black and white squares, it is impossible.
• @Zibbobz: Sure. Once you can make one rectangle with $n=4$ you can just line up as many of those rectangles as you want. Commented May 27, 2015 at 16:40