Reasoning
These are geometric shapes, the number of sides increases, and the words are reversed.
3 elgnairt = triangle
4 erauqs = square
5 nogatnep = pentagon
6 nogaxeh = hexagon
7 nogatpeh = heptagon
8 nogatco = octagon
?
Puzzle 40
You have a very large number of generic plastic building blocks, each in the shape of a cube.
Think about how many cubes you would need in order to construct a giant cube with 16 small cubes along each edge.
If you were to then remove the outside layer, how many small cubes would you have removed?
Reasoning
The original large cube with 16 small cubes along each edge would require 16 x 16 x 16 = 4,096 small cubes.
Removing the outside layer would leave a large cube now with 14 small cubes along each edge (which requires 14 x 14 x 14 = 2,744 small cubes).
It isn't 15 small cubes because you're removing both ends of an edge.
Therefore, you have removed 4,096 – 2,744 = 1,352 small cubes.
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