Question 5
Mason built a pyramid using identical cubes. The pyramid is shown from different angles. He paints the whole pyramid green. How many cubes have exactly 2 faces painted green?
Scan clarification: the internal cube lines are obscured in the original. Use four centred solid square layers, from bottom to top $7\times7$, $5\times5$, $3\times3$, $1\times1$. All exterior faces, including the underside, are painted; touching faces are not painted. This is the interpretation used by the source solution.
Editorial schematic of the stated interpretation (not a new source figure).
Scan clarification: the internal cube lines are obscured in the original. Use four centred solid square layers, from bottom to top $7\times7$, $5\times5$, $3\times3$, $1\times1$. All exterior faces, including the underside, are painted; touching faces are not painted. This is the interpretation used by the source solution.
Editorial schematic of the stated interpretation (not a new source figure).