Ceres has an orbital semi-major axis = 2.768 au. what is ceres’ orbital period?

4.6 years

Explanation:

According to Kepler’s Third Law of Planetary motion “The square of the orbital period  of a planet is proportional to the cube of the semi-major axis (size) of its orbit”:

(1)  

However, if is measured in Earth years, and is measured in astronomical units (unit equivalent to the distance between the Sun and the Earth), equation (1) becomes:  

(2)  

Knowing and isolating from (2):  

(3)  

(4)  

Finally:  

This is Ceres' orbital period

a straight line sloped