## 121. Math Puzzle $6 / 75$

From a long beam of square cross-section (edge length $80 \mathrm{~cm}$), a roller of the largest possible diameter is to be turned.

How large is the wood waste in $\mathrm{dm}^{3}$ and in percent?
The wood waste amounts to $412 \mathrm{dm}^{3}$ or 21.5 percent.