Explanation:

- You have a solid wooden cube.

- A right circular cylinder of maximum possible size is cut from it. This means the cylinder's height equals the cube's side, and its diameter equals the cube's side.

- Let the cube's side be \(s\). So, the volume of the cube is \(s^3\).

- The volume of the cylinder is \(\pi \left(\frac{s}{2}\right)^2 s = \frac{\pi s^3}{4}\).

- The remaining material is the volume of the cube minus that of the cylinder: \(s^3 - \frac{\pi s^3}{4}\).

- Simplifying, the remaining volume is \(s^3 \left(1 - \frac{\pi}{4}\right)\).

- The percentage of this remaining material is \(\left(1 - \frac{\pi}{4}\right) \times 100\%\).

- With \(\pi \approx 3.14\), calculate: \(\left(1 - \frac{3.14}{4}\right) \times 100 \approx 21.5\%\).

- Option 2: 21.5 is the correct answer.

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