The position vector of the centroid of the **tetrahedron** with vertices $A(\vec a), B(\vec b), C(\vec c), D(\vec d)$ is:
- $(\vec a + \vec b + \vec c)/3$
- $(\vec a + \vec b + \vec c + \vec d)/4$
- $(\vec a + \vec b + \vec c + \vec d)/3$
- $(\vec a \cdot \vec b \cdot \vec c \cdot \vec d)$
Show answer and solution
Correct answer: B. $(\vec a + \vec b + \vec c + \vec d)/4$
For a tetrahedron, the centroid divides the line from any vertex to the centroid of the opposite face in ratio 3:1, yielding $\vec g = (\vec a + \vec b + \vec c + \vec d)/4$.