1.
The centre of mass of three particles of masses 1kg1\,\text{kg}, 2kg2\,\text{kg} and 3kg3\,\text{kg} is at (2,2,2)(2, 2, 2). The position of the fourth mass of 4kg4\,\text{kg} to be placed in the system so that the new centre of mass is at (0,0,0)(0, 0, 0) is