1992 AIME 第 7 题

Find the altitudes from $A$ and $D$ to the common edge $BC$

The height from $D$ to plane $ABC$ is its face altitude multiplied by $\sin30^\circ$

The altitudes to $BC$ in faces $ABC$ and $BCD$ are $\frac{2(120)}{10}=24$ and $\frac{2(80)}{10}=16,$ respectively. Because the dihedral angle is $30^\circ,$ the perpendicular height from $D$ to plane $ABC$ is $16\sin30^\circ=8.$ Using face $ABC$ as the base, the volume is $$\frac13(120)(8)=320.$$