With this type of question, you will need to decide on the position of the datum. The 4 answers reference both the nose wheel and also the main wheels, so for simplicity, it is suggested to use the main wheels, as this reduces the amount of calculations required.

The calculations of moments and ultimately, the Centre of Gravity (CG) can be seen in the table below. The datum has been selected in line with the main wheels and all arms are using inches. The question states that the distance between the nose and main wheels is 7 ft 8 inches, but it is normally easier to convert to inches (7'8" = 92 inches) as calculations in feet can prove difficult.

Remember: 1 foot = 12 inches.

Therefore, the aircraft's CG position is 8.3 in forward of the main wheels or 83.7 in. aft of the nose wheel (92 in. - 8.3 in.)

Further information on Moments, Arms and the Centre of Gravity:

The moment is the turning force created around a datum by the mass over a distance or lever arm: Moment = Mass x Arm.

Moments and arms forward of the datum are considered to be negative and those aft of the datum are positive.

The Centre of Gravity (CG) can be found by adding all the moments and then dividing by the total mass: CG = Total Moment / Total Mass.