To calculate the Centre of Gravity (CG) position, the correct formula used is:
Centre of Gravity is defined as:
The point within an object about which the force of gravity is concentrated. Centre of Gravity may also be thought of as the point within an object about which all the moments trying to rotate the object are balanced.
To calculate the position of the Centre of Gravity, the mass and the arm of the stations in the helicopter must be known. Calculate firstly the moments of the weights given at any station in the helicopters weight and balance chart. Thereafter find out the total Centre of Gravity position by adding all moments and all masses on board by using the formula.

CG = Moment / Mass
NOTE:
You might find this question where the Force has replaced the Mass. The force of gravity acting on an object is a measure of the gravitational pull acting on that object. It is a force. Mass is a measure of how difficult it is to accelerate the object. The force of gravity acting on an object can change with location; the mass always stays the same.
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