The diameter and height of the right circular cone will be 4.2 decimeters. â´ The volume of the cone is: \[ \frac{1}{3} \pi \left( \frac{4.2}{2} \right)^2 \times 4.2 \text{ cubic decimeters} \] \[ = \frac{1}{3} \times \frac{22}{7} \times \left( \frac{21}{10} \right)^2 \times \frac{42}{10} \text{ cubic decimeters} \] \[ = \frac{22 \times 21 \times 21 \times 42}{3 \times 7 \times 10 \times 10 \times 10} \text{ cubic decimeters} = 19.404 \text{ cubic decimeters} \] Therefore, the volume of the largest possible solid right circular cone is 19.404 cubic decimeters.