# What kind of puzzle this is?

I received this picture, and the sender told me that it means something?

• One thing that sticks out to me is that if you remove the blocks in reverse order, at no point do any of them fall over - except for removing 6 before 5. – Kevin Apr 25 at 15:54
• nice observation – logo Apr 25 at 16:01
• Could it be said that 11 would topple over once 19 and 18 (and perhaps 17) were removed? That leans on the assumption of the pieces having length, width and depth as well as the mass proportionate to the size of the pieces. – BDrought Apr 25 at 17:31
• I've seen diagrams like this in the fronts of textbooks, indicating which chapters require you to have read which other chapters in order for them to make sense. – Gareth McCaughan Apr 25 at 18:05
• so the answer is the name of the text book!!! – logo Apr 25 at 20:35

I don't know what kind of puzzle, but

During construction in the numbered sequence:

Block 5 is the only piece which needs temporary support, because block 6 is required to support it.

Block 11 is the only piece which needs permanent support, because its C of G is to the right of the right-hand edge of block 10, and
block 12 tips it.
block 13 does not help.
block 14 tips it.
block 15 tips it.
block 16 does not help.
block 17 is not enough to balance blocks 12, 14, 15.
block 18 is still not enough to balance blocks 12, 14, 15.
block 19 does not help because it is centred over the right-hand edge of block 10, which is a fulcrum point.