Two bodies of mass 1 kg and 3 kg have position vectors \(\hat{i}+2\hat{j}+\hat{k}\) and \(-3\hat{i}-2\hat{j}+\hat{k}\), respectively. The centre of mass of this system has a position vector:

\(-2\hat{i}-\hat{j}+\hat{k}\)

\(\vec{R} = \frac{m_1R_1 + m_2R_2}{m_1+m_2} = \frac{1}{4} [-8\hat{i}-4\hat{j}+4\hat{k}] = -2\hat{i}-\hat{j}+\hat{k}\)